Preheat the oven to 450F.
Brush the rolled out dough with 1 tablespoon of the olive oil, then sprinkle it with the garlic slices. Spread the crème fraîche and then cover it with the potato slices, then drizzle those with the remaining olive oil. Sprinkle it with the fresh thyme leaves, crushing them as you sprinkle, and season it liberally with pepper, and lightly with salt.
Bake in the center of the oven until the dough is golden at the edges and the cream is bubbling gently, about 12-15 minutes. Remove, let sit for 5 minutes, add small spoonfuls of the ROE, sprinkle on the red onions then cut and serve.