In a medium saucepan, combine the lentils and water. Bring to a boil, then reduce heat and simmer for 15-20 minutes, until the lentils are tender but not mushy. Drain any remaining liquid and set aside.

In a large skillet over medium heat, heat the olive oil. Add the diced red onion and sauté for 3-4 minutes until softened and fragrant.

Add the minced garlic, cumin, and coriander. Stir and cook for another minute until the spices are aromatic.

Add the cooked lentils to the skillet, stirring to combine with the onion and spices.

Add the chopped spinach and stir gently until just wilted, about 1-2 minutes.

Remove from heat and drizzle with fresh lemon juice. Season with salt and black pepper to taste.

Serve warm as a main dish or side. Garnish with a drizzle of olive oil or fresh herbs if desired.