Step 1

Heat oil in a large pot over medium. Add onion and cook, stirring occasionally, until golden brown and soft, 6–8 minutes. Add garlic, cranberry beans, chickpeas, and turmeric and cook, stirring, until fragrant, about 2 minutes. Add 8 cups cold water and bring to a boil. Reduce heat, bring to a simmer, and cook, stirring occasionally, until beans are halfway cooked (they should still be very al dente), 25–35 minutes. Add lentils and cook, stirring occasionally, until beans are creamy but still hold their shape, and lentils are tender, 25–35 minutes (the soup may look a bit thick, but don’t fret; the greens will release liquid when they’re added, thinning the soup out a bit).

Step 2

Add spinach, cilantro, parsley, and dill and cook until greens are just wilted and have slightly darkened, 4–6 minutes. Stir in lemon juice; season with salt and pepper.

Step 3

While soup is simmering, heat 3 Tbsp. oil in a medium skillet over medium-high. Add onion and cook, stirring often, until golden, 6–8 minutes. Reduce heat to medium and cook, stirring occasionally, until onions are slightly charred and crisp, 14–16 minutes; season with salt. Transfer onions to a plate; cover with foil to keep warm.

Step 4

Meanwhile, mix yogurt and buttermilk in a small bowl; season with salt. (The mixture should have the consistency of heavy cream.)

Step 5

Wipe out skillet and heat remaining 3 Tbsp. oil over medium. Add mint and cook, stirring often, until mint oil is fragrant and slightly darkened, about 1 minute. Transfer to a small bowl or measuring cup.

Step 6

Divide soup among bowls and pour yogurt mixture over soup. Drizzle mint oil over soup, then top with fried onions.