Roasted stuffed squash with herby pistachio salsa

Name: Roasted stuffed squash with herby pistachio salsa
Ingredients: 1 butternut squash (about 750g); 1 tbsp olive oil; 3 garlic cloves unpeeled; large knob of butter; 2 small onions thinly sliced; 2 tbsp red wine vinegar; large pinch of allspice; 150g basmati rice; 75g pomegranate seeds; 150g vegetarian feta crumbled; 75g pistachios finely chopped; 100ml extra virgin olive oil; ½ small bunch of dill finely chopped; small bunch of parsley finely chopped; 1 large green chilli thinly sliced; 1 lemon juiced