Pat the shrimp dry with paper towels and place them in a bowl. Season with half of the Cajun seasoning, garlic powder, onion powder, sea salt, and black pepper.
Slice the andouille sausage into rounds and chop the bell peppers, onion, and celery into bite-sized pieces.
Heat 1 tablespoon of olive oil in a large skillet or wok over medium-high heat. Add the sliced sausage and cook until browned on both sides, about 3-4 minutes. Remove sausage from the pan and set aside.
In the same skillet, add the remaining 1 tablespoon of olive oil. Add the onions, peppers, and celery. Stir-fry for 5-6 minutes until the vegetables are tender-crisp.
Add the seasoned shrimp to the skillet with the vegetables. Cook for 2-3 minutes until the shrimp are pink and opaque.
Return the sausage to the pan and add the cooked brown rice. Sprinkle with the remaining Cajun seasoning and cayenne pepper.
Toss everything together for another 2 minutes until the rice is heated through and the flavors are well combined.
Remove from heat, drizzle with lemon juice, and garnish with fresh chopped parsley before serving.