Arrange the tomato slices on a plate and season lightly with flaky salt. Let rest at room temperature for 15–20 minutes.
In a small bowl, mash the anchovies into the softened butter until completely smooth. Taste before adding salt. Add black pepper if desired.
Toast the bread until deeply golden and crisp. While still hot, rub lightly with the garlic clove.
Spread a thin layer of anchovy butter over the warm toast.
Arrange the salt-cured tomatoes on top, slightly overlapping. Drizzle with olive oil and finish with lemon zest or herbs if using.
Serve immediately while the toast is warm and the tomatoes are at room temperature.