Preheat the oven: Preheat your oven to 180ºC.
Cook the chorizo: Heat the olive oil in a pan over medium heat. Add the chorizo slices and cook until crispy. Remove the chorizo and set aside, leaving 1 tablespoon of the chorizo fat in the pan.
Sauté onions and garlic: Add the diced onion and minced garlic to the pan. Cook over medium heat until the onions are soft and golden.
Prepare the sauce: Add the tomato and roasted red pepper sauce to the onions and garlic, stirring well. Dissolve the stock cube in boiling water to make chicken broth, then pour it into the pan. Stir to combine and simmer for about 5 minutes.
Add spinach and gnocchi: Stir the spinach into the sauce until wilted. Remove the pan from heat and add the gnocchi, mixing well to coat the gnocchi with the sauce.
Combine and bake: Add the chorizo back to the pan, along with the lemon zest and chopped basil. Stir well. Transfer the mixture to an ovenproof dish, top with the torn mozzarella chunks.
Bake: Place the dish in the preheated oven and bake for about 20 minutes, or until the mozzarella is golden and bubbling.