Italian veggie balls

Name: Italian veggie balls
Ingredients: 225g/8oz dried brown lentils; 2 onions, finely chopped; 1 tbsp olive oil, plus a tsp extra for greasing; 4 garlic cloves, crushed; 100g/3½oz baby spinach; 4 tbsp pesto; 1 lemon, zest only; 50g/1¾oz pine nuts, toasted (alternatively use finely chopped almonds or, for a nut-free alternative, the same quantity of whole oats); 1 large free-range egg; 50g/1¾oz fresh breadcrumbs (wholemeal or white); 300g/10½oz dried spaghetti; 2 x 400g tins chopped tomatoes; 2 tbsp tomato purée; 1 tsp red wine vinegar; 1 tbsp granulated or caster sugar; few basil leaves, plus extra to serve; salt and freshly ground black pepper