Mix the flour, salt and yeast in a bowl. Add the water, knead for approx. 10 mins. to form a smooth dough. Cover and leave to rise at room temperature for approx. 3 hrs.
Puree the beetroot with the oil and salt. Flatten the dough a little, shape by hand into a circle (approx. 40 cm in diameter) on a lightly floured surface. Place the dough on a baking tray lined with baking paper, arrange the beetroot on top, add the meat and mascarpone.
Approx. 20 mins. on the bottom shelf of an oven preheated to 240°C. Remove and garnish with thyme.