In a small saucepan on medium-high heat, combine rice with 2 cups of water and a pinch of salt. Bring to a boil, cover, reduce to a simmer and cook until all of the water has been absorbed and the rice can be fluffed with a fork, about 15 minutes.
In a small bowl, combine the spices; chili powder, paprika, cumin, garlic powder, and salt, and stir to combine.
Add raw shrimp to a large bowl, cover with the spice mixture and toss to combine until all of the shrimp are well coated. If time permits, set aside for 15 minutes to allow the shrimp to marinate, however, this step can be omitted if time does not permit.
In a large cast-iron or heavy bottom skillet, warm the olive oil. Add shrimp, arranging them in a single layer, and allow to cook 2-3 minutes per side until cooked through and lightly blackened on both sides. Once cooked, squeeze the juice of 1/2 of a lime over the shrimp.
While the rice and shrimp are cooking, gently heat the black beans and thawed corn in the microwave for 30 seconds to 1 minute. If desired, these ingredients can also be served cold.
Once the rice and shrimp are cooked, assemble the bowls; divide the rice, black beans, corn and shrimp evenly across the bowls.
Top each bowl with salsa, sliced avocado and handful of cilantro to serve.