Preheat the broiler to high.

Roast the tomatoes in a small dish on the highest rack for 10-12 minutes, until blackened.

Spread rock salt on a baking sheet for oyster support.

Shuck the oysters, detaching them from the bottom shell.

Secure each oyster in the rock salt to retain its liquor.

Combine roasted tomatoes and butter in a blender until smooth.

Stir in the shallot.

Place a 1/2 teaspoon dollop of tomato butter into each oyster.

Broil until the tomato butter is melted and the oyster is beginning to darken and curl around its edges, about 8-12 minutes.

Serve immediately.