1 pound brown or large green lentils, rinsed and picked over
10 cups vegetable broth or water
1 jalapeño pepper, stemmed, seeded and chopped
2 teaspoons whole coriander seeds
1 1/2 teaspoons cumin seeds
2 1/2 teaspoons dried oregano
2 bay leaves
2 medium Yukon Gold, russet or red potatoes (1 1/4 pounds total), scrubbed and cut into 1/2-inch dice
10 ounces baby spinach, chopped
1 small butternut squash (1 pound), peeled, seeded and cut into 1/2-inch dice (3 cups)
2 tablespoons olive oil
1 large yellow onion (12 ounces), chopped
2 ribs celery, with leaves, sliced
3 large cloves garlic, finely chopped
1 teaspoon fine salt, or more to taste
1/2 teaspoon freshly ground black pepper, or more to taste
2 lemons
1/3 cup fresh lemon juice