Yellow watermelon and caramel doughnuts

For the doughnuts, place the butter in a pan with the water and bring to a boil. Turn off the heat and stir in the watermelon. In a bowl, mix together the flour, yeast and salt. Make a well in the centre and add the watermelon mixture. Mix until a smooth dough is formed, adding a little water if the dough is too thick. Knead on a lightly floured surface, 10 minutes. Place the dough in an oiled bowl, cover and rest until double in size, 1 hour. Roll out on a lightly floured surface and cut the doughnuts with a 7,5cm round cookie cutter. Cover with a tea towel and leave to rise, 20 minutes.

Heat the sunflower oil in a large, deep pot or deep-fryer to 180°C and fry the doughnuts until golden brown, about 15 minutes. Remove from the oil and drain on paper towel. Repeat with the remaining batter. Set aside to cool.

For the topping, mix the castor sugar, cinnamon and vanilla seeds together.

For the filling, heat the caramel in the microwave, 2 minutes, and leave to cool.

Pierce each doughnut with a small knife on the side. Fill a piping bag with the cooled caramel sauce and fill each doughnut. Roll the doughnuts in the cinnamon-sugar mix, making sure they are coated evenly.