Preheat oven to 170C.
Grease and line 20 cm tart tin with the rolled out short pastry. Line pastry with baking paper & fill base with pastry weights or dried beans.
Blind bake pastry for 10-15 minutes until golden.
Remove paper & weights, lightly brush pastry with one beaten egg, return base to oven for 2 minutes, just to set egg.
Crumble goats cheese into tart shell, spread caramelised onion over cheese.
Whisk remaining eggs and cream together with salt, pepper & thyme, then pour gently into tart case.
Cut cherry tomatoes in half & dot them on top of tart.
Bake around 35-40 minutes, until tart is set and golden.