2 large beefsteak tomatoes
16-ounce ball fresh mozzarella cheese
12 slices white bread, 1/2-inch thick
1 cup prepared pesto
Kosher salt
Unsalted butter, room temperature

Preheat panini grill or griddle

Core the tomatoes and slice tomatoes and mozzarella ¼ inch thick.

Place bread on work surface. Spread each slice evenly with pesto. Place a layer of mozzarella (about 2 slices) on half of the bread and top with a layer of tomato. Sprinkle tomato with salt. Place remaining slices of bread, pesto side down, on top. Spread the top and bottom of each sandwich with softened butter. Grill the sandwiches in batches on the panini grill or griddle for 2 to 3 minutes, until the mozzarella starts to ooze. Cut each sandwich in half and serve warm.