In a Dutch oven or soup pot, heat olive oil over medium heat, add onion and sauté for about 2 minutes, then add carrots and celery, continue cooking for 3 minutes, then add garlic and sauté for another minute.
Stir in oregano, basil and tomato paste. Add fire-roasted tomatoes, vegetable broth, lentils, salt and pepper. Bring soup to a low boil.
Reduce heat and simmer for 25-30 minutes until the lentils are cooked, carrots and celery are tender. Transfer in batches to food processor/blender or use a hand emulsifier and pulse 3-4 times, just enough to create a slight creamy texture and leaving some of the vegetables and lentils whole. Stir in kale and lemon juice. Adjust the seasoning if necessary.
Garnish with fresh basil, oregano and crumbled feta. Serve immediately and enjoy!
