Heat a conventional oven to 350°F / 180°C and line two baking trays.

Rub lemon zest into 75 g sugar. Cream with softened butter and vanilla until pale, then mix in the yolks. Add the combined flour, baking powder, xanthan gum and salt to form a scoopable dough.

Spread one-third of the dough in a bowl and swirl in one-third of the jam. Cover with flattened pieces of the next third of dough and repeat. Finish with the remaining dough and jam. Fold just 2–3 times so the purple streaks stay visible.

Stir cream cheese and 25 g sugar until smooth, then add warm cream and vanilla. Add 1–2 tsp extra cream only if the filling is too firm to spoon.

Scoop 2-tbsp dough portions into the rolling sugar, coat and shape into 14 balls. Space at least 2 inches / 5 cm apart. Press a central well with a 1-tbsp measuring spoon.

Fill each well with about 2–3 tsp cheesecake filling. Bake one tray at a time for 10–12 minutes, until slightly puffed and the filling has set. Keep the waiting tray at room temperature.

Cool completely on the trays before moving.

For the sauce, heat blueberries, 25 g sugar and lemon juice over medium-low heat until juicy. Remove from the heat. Mix cornstarch and water, stir into the fruit, then cook over medium-high heat for 2–3 minutes, stirring until thickened.

Cool the sauce completely. Spoon over the cookies just before serving.