Slice the tomatoes in two slightly above the halfway mark and scrape out the flesh using a corer, then drain on a paper towel.
In the meantime, blitz the basil in a blender with the grated Grana Padano, pine nuts, a pinch of salt and 4-5 tablespoons of olive oil, until the mixture is smooth and creamy.
Cook the couscous according to the instructions on the package. When ready, add the basil and Grana Padano mix and season with salt.
Fill the tomatoes with the couscous and leave in the fridge to rest before serving.