Prepare the pizza dough by pouring the slightly warm water, crumbled brewer's yeast, oil and salt into the bowl of the stand mixer. Operate at minimum speed until the yeast is completely dissolved, then gradually add the flour. Continue kneading until you have obtained a smooth and homogeneous dough, which will tend to detach from the bowl - the same procedure can be done by hand.

Transfer the dough to another large bowl lightly greased with oil, seal with cling film and leave to rise for 8 hours in the oven turned off.

Take care of the onions: clean them and slice them thinly. Transfer them to a non-stick pan and add the sugar. Add the water, mix again and turn on a medium flame. Cook for an hour, stirring occasionally. Turn off the heat and set aside.

Take the dough, place it on a floured work surface and cut it in half. Fill two 28 cm round baking pans well greased with oil. Let the dough rest for another hour, then bake the two pizzas at 200° for 20 minutes.

Remove from the oven and arrange the Provolone Valpadana DOP sweet slices on top. Bake again for 5 minutes, until the cheese is well melted. Cut the pizzas into wedges and place a teaspoon of caramelized onions and the tuna fillets on each. Drizzle with a little oil, sprinkle with thyme and serve.