Prepare the crema. With an immersion or high-speed blender, combine all the ingredients for the crema. Taste to adjust for seasonings, then cover and refrigerate until ready to use.
Prepare the steak. In a small bowl, combine all the ingredients for the chipotle seasoning and set aside.
Cut the steak into bite-sized pieces. If it's too difficult to cut, place the steak into the freezer for 10 minutes to firm up before slicing. Season the meat with a bit of salt and pepper and set aside.
Heat 1-2 tablespoons of neutral oil into a pan on high heat. Once the oil is very hot, add the chopped steak. Cook the meat for 2-3 minutes, flipping so that everything gets a good sear.
Once the steak is seared, sprinkle over the chipotle seasoning, chopped bell pepper, chopped onion, and grated garlic. Cook for 2 more minutes, until the peppers and onions have softened and the steak is cooked to your liking (you may need to lower the heat so the seasoning doesn't burn).
Remove the steak from the heat and serve inside warmed corn tortillas with cheese, the prepared avocado-lime crema, and any other toppings.