Having grown up in the Pacific Northwest I have a special fondness for salmon, particularly wild Copper River King Salmon from Alaska. My mother used to make all kinds of toppings and rubs for grilled salmon and this one is my favorite!
Combine butter, tomatoes, capers, and garlic. Season to taste with sea salt and freshly ground pepper. Transfer to a plastic sandwich bag and refrigerate.
When it's time to grill, let some of the butter come to room temperature. Spread a layer (as much as you want) of butter mixture on salmon before putting the fish on the grill. After removing salmon from the grill and just before serving, spread on a bit more butter mixture.