Heat oil in a Dutch oven over medium-high heat. Add onion, carrot, celery, and beets, and cook for 5-7 minutes, until onions are soft.
Stir in garlic, paprika, salt, and pepper and cook for another minute.
Pour in stock, tomatoes, and lentils. Increase heat to high and bring soup to a boil. Reduce heat to medium-low and simmer for 40-50 minutes, until lentils are cooked and beets are soft.
Stir in kale, lemon juice, dill, and sugar. Cook for another 5 minutes until kale is soft. If the soup is too thick, add more stock or water. Adjust seasonings with more salt and pepper, if needed.
Ladle into soup bowls and garnish with sour cream or plain Greek yogurt.