Warm the milk in a small saucepan to 38 C / 100 F. It should feel just warm on your wrist, not hot.

Combine the flour, yeast, sugar, and salt in the bowl of a stand mixer. Add the warm milk, softened butter, eggs, and lemon zest.

Knead on medium speed for 8 minutes until the dough is smooth, elastic, and pulls away from the sides of the bowl. If mixing by hand, knead on a lightly floured surface for 10 to 12 minutes.

Shape the dough into a ball, place it back in the bowl, and cover with a clean kitchen towel. Leave in a warm spot for 45 to 60 minutes until the dough has doubled in size.

Heat the oven to 190 C / 375 F. Brush a 13x18 inch rimmed sheet pan with melted butter and line with parchment paper.

Halve the apricots and remove the pits. Set aside on a clean cloth.

Turn the risen dough out onto a lightly floured surface. Press and stretch it evenly across the lined pan to fill the edges. If it springs back, let it rest for 5 minutes and press again.

Cover the pan loosely with a towel and let the dough rest for 15 minutes while the oven finishes preheating.

Press the apricot halves cut-side up firmly into the dough in tight rows, fitting them close together across the entire surface.

Bake on the middle rack for 28 to 32 minutes until the edges of the dough are deep golden and the apricots have softened and begun to caramelize at the edges.

Remove from the oven and dust immediately with vanilla sugar while the surface is still hot.

Cool the cake in the pan on a wire rack for at least 15 minutes before slicing into squares or rectangles.