Lay your tomato slices on a large plate, slightly overlapping for a nice presentation. This allows each slice to absorb the flavors from the toppings evenly.
Scatter the chopped capers, artichoke pieces, and finely sliced red onion over the tomatoes. This layer adds texture and a tangy contrast to the sweet tomatoes.
Sprinkle with salt flakes and freshly ground black pepper. Scatter fresh oregano leaves over the top, then drizzle with olive oil and the juice of half a lemon. Let it sit for about 5 minutes so the salt draws out the tomato juices without over-salting.