In a bowl, combine the shrimp and garlic salt.
In a large skillet, melt the butter over medium heat. Add the shrimp and cook, stirring occasionally, until cooked through, about 5 minutes. Transfer the shrimp to a plate. Reserve the skillet.
Add the tomatoes, scallions and cream to the skillet and simmer over low heat for 5 minutes.
Meanwhile, cut the shrimp into bite-size pieces; add to the skillet and cook over medium heat, stirring, until heated through. Season with cayenne pepper and serve over the grits.