1. Heat 2 tbsp olive oil in a heavy-based pan over a low heat. Add the garlic and onion and stir for 10 minutes. Don't let the garlic burn. Bring up to moderate heat and add diced celery and carrot. Stir and cook vegetables until soft.
2. Add tomatoes, tomato paste, herbs, and smoked paprika and 2 cups of water. Simmer for as long as possible, at least an hour, adding water if required.
3. Puree with a stick blender. Season to taste with salt and pepper.