To make the pastry – combine the flour and salt in a medium bowl, place the cubed butter into a small bowl, and then place both bowls in the freezer for an hour.  After the hour, cut the butter into the flour using a pastry cutter until the mix resembles a coarse meal, then make a well in the center of the mix.  In a separate bowl, whisk together the sour cream, lemon juice and water and then add half of the wet mix to the well in the dry mix.  Mix in the liquid until large lumps form, then repeat by adding the rest of the wet – mixing with your fingers at this point is easiest.  Pat the lumpy mix into a ball – do not overwork the dough – then wrap it in plastic wrap and refrigerate for at least an hour (or overnight).

To prep the squash – preheat the oven to 375 and toss the diced squash with the olive oil, lightly salt it with a half teaspoon of salt, and roast on a parchment lined baking sheet for about 30 minutes until the pieces are tender.  Give them a stir part way through if you remember, then set the squash aside to cool a bit – or again, do this ahead and have it covered and in the fridge.

To caramelize the onions – while the squash is roasting, melt the butter in a heavy skillet and cook the onion over low heat with the other half teaspoon of salt and the sugar.  Stir occasionally until the onions are soft and a light golden brown, 30 to 40 minutes.  Stir in the cayenne.  These can also be covered and put in the fridge overnight.

When you’re ready to make the galette – preheat the oven to 400 and line a large baking sheet with parchment.  Combine the squash, caramelized onions, goat cheese and sage in a large bowl.  On a floured work surface, roll out the dough into a 12 to 14 inch round and transfer it to your prepped baking sheet.  Spread the squash mixture into the middle, leaving a 2-inch border, then fold the border over the mixture, the center will be open.  Bake for 30 to 40 minutes until the crust is a lovely golden brown and then remove it from the oven and let it sit for about 10 minutes before sliding it onto a serving platter.  Cut into wedges to serve – the galette is equally marvelous hot or at room temperature.