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I can think of a few things that will help ... but fundamentally there is a conflict between cooking a steak to medium or beyond and having it stay juicy and tender that is VERY hard to resolve. It's just the nature of protein ... animal muscle protein contracts and gets tough when cooked beyond 140 degrees. Only the best, most expensive prime cuts can stay close to tender when cooked to a barely pink medium, and some (myself included) feel that it's kind of a shame to waste good prime beef by cooking it to anything beyond medium-rare. That said, there are some different techniques I suggest for getting a good sear. These are complicated by the stock grates on the Weber One-Touch. The thin plated bars are not at all conducive to creating grill marks or a good sear. They simply don't have the thermal mass and rough surface area needed to really facilitate the Maillard reaction that creates a good sear and that seared flavor. But a few tricks can help. A replacement set of cast iron grates would help more (I have no affiliation with this company at all and I am not recommending them specifically). First, the surface of the steak needs to be really, really dry for a good sear. If there is even the slightest hint of moisture, the surface will generate steam when it hits the grill grate and not sear. The same goes for oil ... although for flavor olive oil is helpful, it actually hinders the searing, so I'd leave it off and just give the grate a light coat of oil (I actually use cooking spray). Patting the surface of the steak with paper towels isn't enough either. One trick I picked up from Cook's Illustrated a few years ago is to season the steak with salt, let it sit for a while to come to room temperature (like 40+ minutes, more on why below; I often let my thick steaks sit salted overnight in the refrigerator), then pat it dry with a paper towel. Then, sprinkle both sides lightly with a mixture of kosher salt and corn starch (equal parts by volume) and place it on an elevated rack in the freezer for 15 to 20 minutes. The key to this is that freezers are extremely dry and usually have air circulating, so this helps dry the surface thoroughly. And the corn starch absorbs any other moisture. Plus, the freezer cools the outside layers of the steak, so when it's back on the grill it will cook a little slower and won't get so tough while the middle, which stays close to room temp, cooks through. The reason that the steak is salted before being dried is to help with the Maillard reaction. This reaction requires amino acids (protein building blocks) and the presence of a reducing sugar to occur. The primary reducing sugar available in steak is the glucose trapped in the cellular fluid. The idea behind salting the steak is to draw some of this cellular fluid to the surface of the meat. As Tubby's Smokehouse points out, the longer salt stays on the surface of the meat, the more moisture is pulled out ... to a point. If left on long enough, the osmotic pressure will equalize and fluid will begin to redistribute back into the steak, bringing seasoning with it (this is the principle behind brining chicken for example). Although there might be a slight net moisture loss, the steak should be more flavorful and the surface will end up with the right compounds to facilitate the Maillard reaction. There's a great explanation of this at the Serious Eats website. Try this method and see if your results are better. With a thin (1" or less) steak the standard sear and then cook over lower heat should work. For thicker steaks (1.5"+) cooked to medium or beyond I actually recommend an opposite approach, starting over low heat and getting a sear at the end. Finally ... I can't emphasize this enough ... get a really good, accurate thermometer. I use a Thermoworks Thermapen but there are less expensive alternatives. Cook to reach the desired intrnal temperature, not the desired look on the outside. After some practice you'll get the timing correct so that a 5-step, 1-flip procedure (On the grill, quarter turn, flip, quarter turn, remove) will give you a nice cross-hatch of grill marks. But until then concentrate on not overshooting your desired temperature and you'll be rewarded with great steak. Good luck and I hope you post some pics!
I'm normally with you -- when I buy a dry aged cut I use salt and barely any pepper before going on the grill. But I tried this on a couple of not-so-great ribeyes from BJ's since this technique is about tenderizing and coaxing more flavor out of a bad cut of meat. I used plain salt on the first and then the rub on the second to see if the flavors were very different. I think the second definitely had more flavor so I'm willing to experiment to see if I can make cheap supermarket steak into something worth buying and eating when it's on sale. I'd love to try a tenderloin or roast on the rotisserie with the Penzey's rub though.
I tried this with a couple of thick ribeyes over two days. It worked well -- a much better way of getting flavor into the meat than simple marinading. An important thing to know though: I am considered my many to be a heavy salt user so your tastes may vary. But I will say that my wife -- who never uses salt -- found the taste acceptable. Anyway, I used some flavors other than plain salt as a couple of websites have suggested. I started with a light dusting of Penzy's English Prime Rib Rub, added some hot paprika on top, then covered in kosher salt until it was fully covered. I wrapped the steaks in plastic wrap and let them sit for an hour. Then I rinsed them and grilled them. Very flavorful! I'm going to see if I can perfect the rub this summer because I'm a fan of this technique now. I also think I need to play with the timing though. Like nay brining technique, varying the time can change the amount of flavor, especially for thin cuts.