There are, of course, gazillions of possible toppings. The broiling time will depend on your appliance.

4 medium ripe tomatoes, cored and halved vertically, or sliced vertically into thirds.

Topping 1:
4 garlic cloves, mashed
1 t Dijon mustard
1/2 t dry mustard
2 t olive oil
salt and pepper, to taste

Topping 2:
4 ounces blue cheese, crumbled (about 1 cup)
1 T minced fresh parsley
pepper, to taste

Topping 3:
1/4 c mayonnaise
1/4 c minced onion, shallot, or scallion
2 T minced fresh parsley
pepper, to taste

1. Adjust the oven rack so that it is about 6 inches from the broiling element. Preheat the broiler. Place the tomato halves or slices on a lightly oiled, rimmed baking sheet and set aside briefly.

2. Combine the three topping ingredients to the desired consistency. Pat the mixture over the tomatoes–only on one side of the slices.

3. Broil the tomatoes, watching them carefully to make sure they are not burning, just until they soften a bit and the tops become nicely browned, 5 to 6 minutes. Serve hot or warm.