In short: A savoury galette on shortcrust pastry with tomatoes and caramelised onion. The dough is made with cold butter and yoghurt, and the onion is caramelised in advance — its sweetness is what carries the flavour.
The pastry
1.5 cups flour — better as 1 cup plain and ½ cup wholemeal — 110 g cold butter in cubes, 2 tbsp Greek yoghurt (5 %), 4–5 tbsp cold water, 1 tsp salt, ½ tsp dried rosemary or thyme.
Combine the flour with the cold butter, salt and rosemary in a food processor or with a paddle attachment. Without a machine, simply chop it with a knife so the butter pieces stay about the size of small beans — that is what gives the dough its layers.
Mix the yoghurt with the cold water, add to the flour and bring together. Wrap the dough in film, flatten it slightly and rest it in the fridge for a couple of hours.
The filling
Two onions, red or white, 1 tbsp butter, 1 tbsp olive oil, tomatoes, thyme and an egg yolk for glazing.
Slice the onion into thin half-rings and cook slowly in a mixture of olive oil and butter until genuinely caramelised. This takes longer than most people expect, and rushing it is the difference between sweet onion and merely cooked onion.
Assembly and baking
Roll the dough into a round 4 mm thick. Pile the onion in the centre and spread it out, leaving a clear border. Arrange the tomatoes over it, scatter with thyme, fold the edges of the pastry inwards over the filling and brush the pastry with egg yolk.
Bake for around 40 minutes at 180–200 °C. Time and temperature vary between ovens.
Frequently asked questions
Why is the base of my galette soggy
The filling went onto raw dough with nothing between them. A layer of breadcrumbs or grated cheese under the tomatoes solves it.
Does the dough have to be chilled before baking
Yes. Cold dough holds its shape and stays layered; warm dough spreads on the tray.
What can replace Greek yoghurt
Thick sour cream. The job is the same: acidity and moisture without loosening the dough.