Heat 2 tablespoons extra virgin olive oil in a large pot over medium heat. Add 1 yellow onion, 2 carrots, and 2 ribs celery. Cook about 4 minutes, stirring often, until soft.
Add 4 cloves garlic (grated), 1 teaspoon ground cumin, ½ teaspoon ground turmeric, and 1 teaspoon dried oregano. Stir for 1 minute until fragrant.
Add 2 cans lentils (drained and rinsed) and pour in 4 cups vegetable broth. Season with ¾ teaspoon salt and ¼ teaspoon black pepper. Stir well and bring the soup to a gentle simmer (small bubbles).
Let the soup simmer uncovered for 15 minutes, stirring once or twice, so the flavors blend together. Stir in 4 cups spinach until wilted. Turn off the heat and add zest and juice of ½ lemon.
Taste and adjust for salt and lemon. Serve warm, with feta and a drizzle of olive oil on top if you like.
