Spicy Lentil Soup

2 cups red lentils, picked over and rinsed

1 serrano chile pepper, chopped (remove seeds for less heat)

1 large tomato, roughly chopped

1 1 1/2-inch piece ginger, peeled and grated

3 cloves garlic, finely chopped

1/4 teaspoon ground turmeric

Kosher salt

1/4 cup roughly chopped fresh cilantro, plus more for topping

1/4 cup Greek yogurt

Naan or other flatbread, for serving