Peel onion and garlic. Chop the onion finely. Chop garlic finely. Melt butter in a pot. Fry onion, garlic and rice in it until transparent. Season with salt and pepper.
Deglaze with 250 millilitres of vegetable stock. Cook for ten minutes at low heat. Add 500 millilitres of vegetable stock, stirring gradually. Meanwhile grate cheese. Clean the rocket, wash and pat dry.
Clean, wash and halve the tomatoes. Heat the oil in a pan and sauté the tomatoes. Add cheese to the risotto and fold in. Carefully fold in rocket and tomatoes as well. Arrange on plates and garnish with black pepper.
Sprinkle with pecorino slicer.