In a large pot over medium heat, add the olive oil, onion, and ½ teaspoon salt. Cook until softened, about 3 minutes. Stir in the cumin and garlic and cook for 30 seconds, stirring often.
Add the beets, potato, water, ½ cup pumpkin seeds, and remaining 1 teaspoon salt. Bring to a boil, then simmer, covered, for 25-30 minutes, or until the veggies are tender.
While the soup cooks, add the remaining ½ cup pumpkin seeds to a skillet over medium heat. Toast the seeds (no oil needed), stirring occasionally, until they start to pop, about 2-4 minutes. Remove from heat and set aside.
Transfer the soup to a blender and blend until smooth, being careful to let the steam escape (if it’s too much liquid for your blender, remove some of the liquid or do it in two batches). Pour the soup back into the pot and stir in the vinegar. Taste and add more salt or vinegar, if needed.
Serve topped with about ½ cup yogurt (stir it in slightly), toasted pumpkin seeds, fresh herbs (if using), and black pepper. A side of buttered toast is really nice with this soup!