Heat the olive oil in a medium pot over medium heat and toast the cumin seeds until they begin to sizzle and become aromatic.
Add the diced yellow onion to the pot and sauté for 5 to 7 minutes until the edges are golden brown and translucent.
Stir in the ginger and garlic pastes, cooking for 1 minute to release their fragrance without burning.
Add the diced chicken breast to the pot, searing the pieces until they are lightly browned on all sides.
Stir in the tomato puree, turmeric, ground coriander, chili powder, and sea salt, mixing well to coat the chicken.
Add the rinsed red lentils and water to the pot, then bring the mixture to a gentle boil.
Reduce the heat to low, cover with a tight-fitting lid, and simmer for 15 to 20 minutes until the lentils are soft and the chicken is fully cooked.
Remove the lid and fold in the fresh spinach, stirring until the leaves are just wilted into the curry.
Garnish with freshly chopped cilantro and serve warm.