Slice the skirt steak into roughly 3-inch (7-cm) pieces. Transfer the pieces to a medium bowl.
2. Step
Thinly slice the pork shoulder, then transfer the pieces to a separate medium bowl.
3. Step
Pound the chicken thighs flat, then slice them in quarters. Transfer the pieces to a third medium bowl.
4. Step
In a small bowl, combine 2 tablespoons salt, 1 tablespoon pepper, paprika, chili powder, cumin, garlic, and lime juice. Stir until there are no lumps.
5. Step
Evenly divide the marinade among the 3 bowls of chicken, steak, and pork.
6. Step
Toss the meats until they are evenly coated, then refrigerate for at least 30 minutes.
7. Step
Preheat the oven to 300°F (150°C). Line a baking sheet with parchment paper.
8. Step
Place 3 onion halves in the middle of the baking sheet, then insert a skewer in each onion, evenly spaced, near the inner edges.
9. Step
Thread a piece of chicken onto one skewer, then a piece of steak onto the second, followed by a piece of pork onto the third. Repeat with the rest of the meat.
10. Step
Secure another onion half onto the tops of the skewers to hold the towers together.
11. Step
Bake for about 1½ hours, until the meat is slightly brown on the edges.
12. Step
Increase the oven temperature to 450°F (230°C).
13. Step
On one side of the baking sheet, toss the bell peppers and sliced onion with the remaining ½ tablespoon of salt, remaining ½ tablespoon of pepper, and the oil.
14. Step
On the other side of the baking sheet, spread out the tortillas. Cover the tortilla side with foil.
15. Step
Bake for 15 minutes, until the edges of the meat and the vegetables are slightly charred.
16. Step
Slice your meat of choice into a tortilla, add vegetables, and top with guacamole, sour cream, pico de gallo, and a squeeze of lime.
