One Tray Bolognese Bake

• 3 celery stalks, cut into 4 pieces
• 2 carrots, cut into 3 pieces
• 3 garlic cloves
• 1 brown onion, cut into quarters
• 400 g tin lentils, drained
• 500 g beef mince
• 800 g tin diced tomato
• 2 tbsp tomato paste
• 3 tbsp smoked paprika
• 2 tbsp ground cumin
• 2 tbsp balsamic vinegar
• 3 tbsp olive oil
• 500 ml vegetable stock
• 375 g spaghetti
• 0.25 cup grated parmesan to serve