Preheat the oven to 220ºC/gas mark 7. Put the naan breads on a large baking sheet. In a small bowl, mix the tikka paste and soured cream, then spread over each naan bread, leaving a 2cm border.
Heat half the oil in a lidded frying pan. Add the chopped onion and crushed chilli and cook for 30 seconds until softened. Stir in the spinach and season with freshly ground black pepper. Cover and cook until the spinach has wilted, then transfer to a sieve and press out any excess liquid from the spinach with the back of a spoon. Roughly spread the spinach mixture over the naan breads, then scatter over the paneer and sliced onion.
Drizzle over the remaining oil and bake in the oven for 10-15 minutes. Season with freshly ground black pepper, then serve one pizza per person with salad on the side.