In a large skillet, melt ghee over medium-high heat. Add the shrimp and onion, and cook, until the shrimp is pink; remove from skillet. In the same skillet with the remaining ghee, add kale and bell peppers; cook 4 to 6 minutes, stirring occasionally, until softened. Add shrimp back to skillet.
Sprinkle in next 5 ingredients (cumin through salt/pepper). Add olives, and cook and stir for 1 to 2 minutes. Remove skillet from heat and set aside. To serve, scoop the shrimp mixture into the lettuce leaves and top with sliced avocado.