Preheat the oven to 200oc.
Cut two circles out of the pastry as large as you can get. Place onto a baking tray. Mix the mascarpone cheese with the parmesan and egg yolk. Season with salt and pepper.
Spread the cheese mixture over the shortcrust pastry leaving a gap between the mixture and the edge of the pastry.
Slice the baby tomatoes in half then keeping in colour order, start laying the tomatoes cut side up in circles working from the outside edge inwards, each circle being of a different colour.
Once the tart is full, bring the edges up and fold over creating a little bowl effect.
Season with cracked black pepper and a little extra parmesan cheese then drizzle a little olive oil over the top.
Place into the oven for 20-25 minutes until cooked. Garnish with a few fresh basil leaves.