Combine the all-purpose flour, egg yolk, water, plain Greek yogurt, olive oil, and 1/2 tsp salt in a mixing bowl.

Knead the dough until smooth, then shape it into a ball.

Chill the dough ball in the refrigerator for 30 min.

Roughly chop the ripe tomatoes, garlic, and yellow onions on a cutting board.

Cook the yellow onions with the remaining olive oil in a saucepan over medium heat until soft and lightly caramelized.

Add the chopped tomatoes, garlic, tomato paste, sugar, and remaining salt to the saucepan.

Simmer the tomato mixture over very low to medium heat for 60 min, stirring regularly.

Remove the tomato confit from the heat once most of its liquid has evaporated.

Roll out the chilled dough and place it in the tart pan.

Prick the dough base all over with a fork, then spread the tomato confit evenly over it.

Arrange the Kalamata olives and optional tomato slices over the filling.

Bake the tart at 180°C / 350°F for 40 min until the crust is crisp and browned underneath.

Top the baked tart with anchovy fillets and fresh basil.

Serve warm or at room temperature.