Preheat the oven to 500 degrees F. Generously season both sides of steak with salt and pepper. Put a large cast-iron skillet over high heat. When it is very hot, add the steak to one side of the pan and tomatoes, almonds, garlic, and jalapenos, if using to the other. Sear the steak for 3 to 5 minutes, stirring the tomato mixture once or twice.
Once a nice crust has formed on one side of steak, turn it over, carefully transfer the now-charred tomato mixture to a food processor, and put pan in oven. If tomatoes are not a bit blackened, leave them in pan and check again after a minute or two in the oven. Cook until steak is rare to medium-rare, about 6 to 12 minutes longer depending on its thickness (an instant-read thermometer will register 125 degrees F when steak is medium-rare). Transfer the steak to a plate and let it rest for 5 to 10 minutes.
While the steak is cooking or resting, add the vinegar and olive oil to the tomato mixture in a food processor, and season with salt, pepper and pimenton or chili powder, if using. Process the mixture, adding more olive oil or vinegar as you like, until the mixture reaches the desired consistency. Sauce should still be a little crunchy from almonds.
Slice steak thinly, against the grain. Serve with sauce.