Cut the chicken breast into uniform 1-inch cubes to ensure even cooking.
Warm the avocado oil in a deep skillet or Dutch oven over medium heat until shimmering.
Add the diced onion, minced garlic, and grated ginger, sautéing for 3-4 minutes until the onion is soft and fragrant.
Place the chicken cubes in the pan and sear for 5 minutes, stirring occasionally until golden on the outside.
Mix in the dry red lentils, curry powder, turmeric, sea salt, and black pepper, stirring for 1 minute to toast the spices.
Pour in the water, scraping the bottom of the pan to release any browned bits, and bring to a boil.
Reduce heat to low, cover, and simmer for 15-18 minutes until the lentils have absorbed the liquid and softened.
Stir in the light coconut milk and fresh spinach, folding gently until the leaves are wilted and the sauce is velvety.