In the bowl of a stand mixer, combine the warm water, the yeast and the sugar. Let stand for 5-10 minutes, until you see bubbles forming.
1 cup warm water, 2 tsps active dry yeast, 1 tsp sugar
Add the flour, 1/4 cup of the olive oil, and the salt. Mix on low speed using the dough hook attachment of your stand mixer for a few minutes until the dough is smooth. It will be a little sticky; this is normal.
3 cups all purpose flour, 1 tsp salt, 1/4 cup Greek olive oil
Remove the dough from the bowl and shape it into a ball. Transfer your dough to a bowl that you have brushed with olive oil.
Cover the dough with plastic wrap and place it in a warm, draft free location for approximately 1 hour, until it has doubled in size.
Spread 2 tablespoons of olive oil onto the bottom of your baking pan. Punch the dough down a bit, and transfer it to the baking pan. Using your fingers, stretch it into a rectangle; it doesn't have to be perfect. Keep stretching until you've covered most of the bottom of the pan.
Cover the dough loosely with plastic wrap, place in a warm draft-free location and let it rise again for another 20 minutes.
Preheat your oven to 400°F.
In a bowl, combine your sliced red onions, the slivered red tomatoes, the olive oil, salt, pepper, sugar and oregano. Stir carefully to combine.
1 large red onion, thinly sliced, 2 medium size ripe (but not watery) tomatoes,, 1 tsp salt, 1/4 tsp pepper, 1 tbsp dried Greek oregano, 1 tsp sugar, 1/4 cup Greek olive oil + 2 tablespoons (for the pan)
Spread all the vegetables over the dough in the baking pan, keeping most of the liquid behind in the bowl. Discard liquid, or dip some bread in it, and enjoy.
Bake in the middle rack of your oven for 40-45 minutes, or until the underside of your dough and the edges are golden brown, and the vegetables have caramelized.
Remove from the oven, and let your ladenia sit for 5-10 minutes to cool. Transfer it to a wire rack to allow it to cool for another few minutes, before serving. Enjoy!