Mix the spice blend. In a small bowl, combine chili powder, cumin, smoked paprika, garlic powder, oregano, cayenne (if using), 1 teaspoon salt, and several grinds of black pepper. Set aside.

Prep the veggies. Slice peppers, onion, zucchini, and mushrooms into even pieces so they cook at the same rate. If using frozen corn, run it under warm water and pat dry so it sears instead of steams.

Cook the vegetables. Heat a large skillet over medium-high. Add oil, then the onion and peppers. Cook 3–4 minutes, stirring occasionally, until slightly softened and lightly charred at the edges.

Add zucchini, mushrooms, and corn. Cook another 4–5 minutes, letting the veggies sit undisturbed in the pan for 30–60 seconds at a time to build color. You want some browning for flavor.

Season the veggies. Sprinkle the spice blend over the vegetables and toss to coat. Cook 1–2 minutes to toast the spices. Taste and adjust salt, pepper, and heat. If using black beans, stir them in now and warm through.

Make the lime crema. In a bowl, whisk sour cream (or yogurt), lime zest, lime juice, mayonnaise (if using), and a pinch of salt. It should be pourable but not runny. Add an extra squeeze of lime or a teaspoon of water to loosen if needed.

Warm the tortillas. Heat a dry skillet over medium and warm each tortilla for 20–30 seconds per side until pliable with a few light char spots. Keep them wrapped in a clean kitchen towel so they stay soft.

Assemble the tacos. Fill each tortilla with the spiced veggies (and beans if using). Add avocado, a drizzle of lime crema, cilantro, radishes, and cheese. Finish with a squeeze of lime and a few drops of hot sauce.

Serve immediately. Tacos are best hot and juicy. Put extra crema and lime wedges on the table for topping as you eat.