Greek Tomato Salad

to 4 pounds ripe tomatoes, preferably heirloom

small red onion, sliced thinly crosswise

or 2 small sweet peppers, such as bell or corno di toro, sliced into thin rings

Flaky sea salt, such as Maldon

Greek feta cheese

roughly chopped mint

dried oregano

Fruity extra-virgin olive oil, for drizzling