Cut the tomatoes in half across the middle. Grate each half on the coarse holes of a box grater into a 2 L / 2-quart bowl, pressing the cut side against the grater until only the skin is left in your hand. Discard the skins, then stir in 1 tablespoon of the olive oil and the salt. The tomato should taste fresh and lightly salty.
Set one rusk on each of four 20 cm / 8-inch plates. If your rusks are rock hard, hold each one under running tap water for 2 seconds, then shake off the drips. Don't soak them longer, or they'll turn to mush.
Spoon a quarter of the grated tomato and its juice over each rusk, starting with the juice so it soaks in. Let the plates sit for 10 minutes. Press the center of a rusk with a fork. It should give a little, with a soft outside and a slight bite in the middle.
Crumble about 35 to 40 g of feta over each rusk, then scatter on 3 olives and a quarter of the capers. Sprinkle each plate with 1/4 teaspoon of oregano and drizzle the remaining 3 tablespoons of olive oil evenly over the four plates. Serve within 30 minutes.