Savoury Masala Oats

1 tbsp coconut oil
1 onion, sliced
1 carrot, finely chopped
1 tsp mustard seeds
1 tsp turmeric
1 tsp cumin seeds
1 tsp ground coriander
½-1 tsp chilli flakes
2 cloves garlic, sliced
1 knob ginger, minced
10 cherry tomatoes, sliced
150g steel cut oats
2 pints water
2 cups peas
½ tsp sea salt
Black pepper, to taste
½ tsp garam masala
1 lemon, zested