Cook the rice: Rinse rice until water runs mostly clear. Add rice, water (or broth), salt, and olive oil/butter to a pot. Bring to a boil, cover, reduce heat to low, and cook 15 minutes (or per package). Rest 5 minutes, then fluff. Stir in lime zest, lime juice, and chopped cilantro.
Mix the slaw: Toss cabbage and shredded carrot with lime juice, olive oil, and salt. Set aside to soften slightly.
Make the creamy lime sauce: Stir together Greek yogurt (or sour cream), mayo (if using), lime juice, garlic powder, and a pinch of salt. Add 1–2 tsp water if you want it drizzlier.
Season the fish: Pat fish dry (this helps the crust stick). Rub with olive oil, then coat evenly with blackening seasoning and salt (only if needed).
Cook the fish: Heat a skillet over medium-high heat. Cook fish 3–4 minutes per side (depending on thickness) until blackened and flaky. Let rest 2 minutes, then break into chunks.
Warm the add-ins (optional): Quickly warm beans and corn in the microwave or in the skillet after the fish.
Build bowls: Add rice to bowls, top with slaw, blackened fish, beans, corn, pico, avocado, and a drizzle of creamy lime sauce. Finish with cilantro and lime wedges.