To prepare Ryann's spicy grilled fish tacos recipe, preheat the grill to medium-high heat. Place the fish fillets in a large skillet and season with salt and pepper to taste. Heat the oil in the skillet over medium heat and add the garlic. Cook and stir for 2 to 3 minutes, until fragrant. Add the onion and cook until softened, about 3 to 4 minutes. Stir in 2 tablespoons of the lime juice and 1 teaspoon of kosher salt. Pour the mixture into the tortillas and top with the remaining ingredients. Bake for 10 to 15 minutes or until fish flakes easily when pierced with fork. Serve with sour cream and guacamole.