Prep the peppers: Heat the oven to 400°F (200°C). Slice peppers in half lengthwise, remove seeds and membranes, and place cut-side up in a baking dish.
Brush with a little olive oil and sprinkle with salt.
Pre-bake the peppers: Bake for 12–15 minutes until slightly softened. This helps them cook through without overbaking the shrimp later.
Make the yogurt-lime sauce: In a small bowl, stir together Greek yogurt, lime juice, a pinch of salt, and a dash of chili powder. Refrigerate until serving.
Sauté aromatics: Warm 1 tablespoon olive oil in a large skillet over medium heat.
Add onion and cook 3–4 minutes until translucent. Stir in garlic for 30 seconds until fragrant.
Add the base: Stir in black beans, corn, diced tomatoes with green chiles, and cooked quinoa or rice. Season with taco seasoning, 1/2 teaspoon salt, and black pepper.
Cook 3–4 minutes to meld flavors.
Add shrimp last: Fold in chopped shrimp and cook just until pink and opaque, 2–3 minutes. Squeeze in the lime juice and stir in cilantro. Taste and adjust seasoning. Do not overcook the shrimp.
Fill the peppers: Spoon the hot shrimp taco mixture into each par-baked pepper half, packing it slightly so it mounds.
Add cheese (optional): Sprinkle with shredded cheese or crumbled cotija.
Return to the oven for 6–8 minutes, until the cheese melts and peppers are tender.
Finish and serve: Top with a drizzle of yogurt-lime sauce, avocado, jalapeño slices, and extra cilantro. Serve with lime wedges and hot sauce.