2 large beefsteak or other tomatoes
Kosher salt, freshly ground pepper
8 slices sourdough bread or other country-style loaf
¼ cup mayonnaise
1 pound sharp white cheddar, coarsely grated
1 small shallot, very thinly sliced
- Slice tomatoes as thin as possible (a serrated knife works great) and place on a wire rack set inside a rimmed baking sheet; season with salt and pepper. Let sit, turning once, until they have released some of their liquid, 20–30 minutes.
- Heat 2 dry large skillets over low (or use 1 skillet and work in 2 batches). Spread 1 side of 4 slices with half of mayonnaise. Set slices, mayo side down, on a cutting board. Mound cheese on slices, pressing down gently to pack onto bread. Top with shallot and close sandwiches.
- Cook, mayo side down, pressing gently, until bottom sides are golden brown (you should barely hear any sound of sizzling as the bread hits the skillet; low and slow is key), 6–8 minutes. Spread remaining mayonnaise over top slices of bread and carefully turn sandwiches over. Cook until other side is golden brown and cheese is melted, 6–8 minutes.
- Transfer to a cutting board and carefully pry each sandwich open. Add a thin layer of tomatoes and close back up; slice in half.