In a large saucepan, bring the water and salt to boiling. Gradually stir in the grits. Simmer, uncovered, for 5 to 7 minutes or until thick, stirring frequently. Remove from heat; stir in garlic-flavored cheese and butter until melted. Stir in slivered onion, milk, and eggs. Transfer mixture to a 2-quart rectangular baking dish. Bake, uncovered, in a 350 degree F oven for 40 minutes.
Sprinkle snipped basil over baked grits. Arrange tomato slices over basil. Sprinkle with cheddar cheese and Monterey Jack cheese. Return to oven and bake 5 minutes more. Let stand 10 minutes before serving. Makes 8 servings.