Cook the beans: Heat olive oil in the pressure cooker pot insert using the sauté function. Add onion and a generous pinch of salt. Cook, stirring regularly, until onion is tender and golden brown, 16-18 minutes. Add garlic and cook, stirring constantly, 1 minute. Add dried beans, turmeric, and 1 tsp freshly ground pepper. Stir to coat. Cover with water by 1-½ inches. Secure the lid, and cook for 40 minutes on high pressure. Allow the pressure to naturally release.

Add remaining ingredients: Stir in lentils and cook, stirring occasionally, until beans and lentils are completely tender, 25-35 minutes. The soup should be thick. Add spinach, cilantro, parsley, and dill and cook until greens are just wilted and have slightly darkened, 4-6 minutes. Stir in lemon juice and season with salt and pepper. Set aside and keep warm.

Caramelize the onions: Meanwhile, heat 2 tbsp oil in a medium skillet over medium-high. Add onion and cook, stirring often, until golden and caramelized, 16-18 minutes. Season with salt and set aside.

Prepare the yogurt: Mix yogurt, buttermilk, and a pinch of salt in a small bowl.

Prepare the mint oil: Wipe out skillet and heat remaining 4 tbsp oil over low. Add mint and remove from heat. Let steep for at least a few minutes until mint oil is fragrant.

Assemble and enjoy: Divide soup among bowls and drizzle with yogurt mixture and mint oil. Top with caramelized onions.