Place the 1 head of peeled garlic, 2 chopped onions, 1 chopped red chilli and 1 thumb of peeled ginger into a blender and blitz into a chunky paste.
Heat the 1 tablespoon vegetable oil in a deep pan over a medium heat. Toss in the 1 teaspoon cumin seeds, 1 teaspoon coriander seeds, 2 cardamon pods and stick of cinnamon into the pan. Toast the spices for around a minute until they begin to give off a fragrant aroma.
Now add the curry paste into the pan. Fry for about 5 minutes until the onions are soft and the paste has lost most of its moisture.
Add the 1 teaspoon sugar and 1 teaspoon turmeric into the pan. Then pour in the 1 can of coconut milk, 1 can chopped tomatoes, 250g red lentils and 100 ml of water. Stir the pan to combine all the ingredients then bring the pan to a simmer. Cover and cook for 20 minutes or until the lentils are soft with a little bite. The sauce should have thickened considerably, if it's too thick just add a little more water and stir to loosen.
Season to the sauce to taste and serve with fresh basmati rice or a warm naan.