Heat a non-stick frying pan on a medium heat and dry fry the halloumi cubes for around 2-3 minutes on each side until they begin to brown. There's no need to add any oil. Once done, turn off the heat and put the halloumi to one side.
In a food processor or blender, add the vegetable oil, onion, garlic, ginger, chilli, and all the spices - tumeric, cumin, garam masala, ground coriander and cayenne pepper.
Blend until you have a paste - around 1 minute. If you feel it's not binding together you can add a splash of water.
In another non stick pan, add the paste and cook over a medium heat for around 5-10 minutes as the onions begin to soften and the spice paste turns golden brown.
Then add a vegetable stock pot or cube and make sure it's incorporated, before adding the tinned tomatoes. Add water half way up in the tin to loosen the remaining tomatoes, and pour into the pan. Give the ingredients a good stir and turn down the heat to low and simmer for five minutes.
Once the curry has simmered for five minutes, add the frozen spinach. And continue to simmer for a further 10 minues until the spinach wilted, stirring occasionally. If you're using fresh spinach you can add this at the same time as the halloumi.
With five minutes cooking time left, add the halloumi and stir into the curry sauce. Simmer for another five minutes. And before serving, squeeze some lemon juice over the top, and sprinkle with some freshly chopped coriander.