Whisk together the milk, eggs, cayenne, salt and pepper. Stir in the cheeses. Spoon mixture into 6 six-ounce ramekins. Place ramekins in a shallow pan and pour hot water around them to a depth of 1 inch. Bake in preheated 350 F oven for 45 minutes until lightly browned.
While timbales bake, prepare the tomato coulis. Heat the butter or olive oil in a nonreactive pan and saute the onion and garlic until softened. Add the tomato paste, water, thyme, salt and pepper. Stir to blend all ingredients and simmer 3-4 minutes.
Timbales may be served in the ramekins or turn out onto small plates. Spoon the warm tomato coulis over or around the timbales.
Note: Tomato coulis is delicious on poached chicken or fish.