Bring broth or water to a gentle boil in a medium pot. Slowly whisk in the grits, reduce heat, and cook according to the package directions, stirring frequently.
When the grits are creamy, stir in butter and cheddar. Cover them on low heat while you cook the shrimp.
Toss shrimp with Cajun seasoning. Heat olive oil in a skillet, add bell pepper, and cook for 2 minutes.
Add shrimp and cook for 1 to 2 minutes per side, until pink and opaque. Add green onions during the final minute.
Spoon the cheesy grits into bowls and place shrimp on top. Finish each bowl with a squeeze of lemon.
