Upside Down Tomato Tart

Upside down cakes are traditionally dessert fare, made with apples, but this tart is a combination of sweet and savory mediterranean flavors: Perfect to delight your guests on a weekend dinner!
This lovely recipes I saw at by Nina and I like it.

You Will Need:

The filling: 
3 lbs (1.5 kg) Roma tomatoes
3 red onions  
2 cloves garlic 
2 sprigs fresh thyme  
2 teaspoons (10 g) butter 
2 tablespoons cane sugar Olive oil 

The dough:
3 cups (300g) flour 
1/2 cup (10cl) olive oil 
1 egg yolk
2 pinch of salt Fresh thyme, 
3 pinches