In a medium saucepan, melt butter. Whisk in flour and cook for 1 minute. Gradually whisk in milk until smooth. Bring to a simmer, stirring constantly. Reduce heat and simmer for 5 minutes, or until thickened.
Remove from heat and stir in Gruyere cheese until melted. Season with salt and pepper. Whisk in eggs one at a time until well combined.
Place one pie crust in a 9-inch pie plate. Pour in the cheese sauce and top with bacon and tomatoes. Cover with the second pie crust and crimp the edges to seal.
Bake for 40-45 minutes, or until golden brown and set. Let cool slightly before slicing and serving.
Notes
Serve warm and enjoy! Consider adding a sprinkle of paprika before baking for extra flavor and color.