Slow-cooker tandoori beef masala

Name: Slow-cooker tandoori beef masala
Prep time: 10 min
Total time: 10 min
Cuisine: Asian, Indian
Ingredients: 400 g lean casserole beef; 2 small onions (or 1 large); 1 tbsp mild Tandoori curry powder; 2 cloves garlic (finely chopped or crushed (or 1 tsp lazy garlic)); 1 thumb-sized piece of ginger (peeled and finely chopped (or 1 tsp lazy ginger)); 500 ml water; 1 tin chopped tomatoes; 1 cup red lentils; 1 large sweet potato (peeled & chopped into small chunks); 1 fresh green chilli (finely chopped); juice of 1 lime; fresh coriander; salt and pepper; low calorie cooking spray