Step 1

In a bowl large enough to hold the steak, combine 1 Tbs. of the oil, the lime juice, tequila, garlic, sugar, chile powder, cumin, and 1/2 tsp. salt. Add the steak and turn to coat.

Step 2

Heat a 12-inch cast-iron skillet over medium heat for 2 minutes, then add 1 Tbs. of the oil. Increase the heat to high, and add the peppers and onion to the skillet. Cook, stirring occasionally, until they begin to brown in spots, 7 to 8 minutes. Remove from the skillet, transfer to a plate, season with salt and pepper, and set aside.

Step 3

Add the remaining 1 Tbs. oil to the skillet. Add the steak and cook over medium-high heat, flipping once, until just cooked through, about 8 minutes. Transfer to a cutting board. Return the onions and peppers to the skillet. Add 1/4 cup water, and stir to loosen any browned bits stuck to the bottom of the pan; keep warm.

Step 4

Thinly slice the steak against the grain, and sprinkle with a little salt. Toss with the vegetables in the skillet and any meat juice. Serve with the tortillas, avocado, sour cream, cilantro, and lime wedges.