Baking really brings out the complex flavors of pluots and highlights their beautiful color. This is a gorgeous and delicious dessert that is quite simple to make.
Make the dough: Cut 8 oz. of cold butter into small chunks. Combine with 2 C. all-purpose flour in a large bowl and work together with your fingers (or use a pastry blender). You should end up with pea-sized pieces of dough.
In a small bowl, whisk together 1 egg yolk and 2 T. cold water. Combine with the flour/butter mixture and mix or stir until combined. Press into a ball and refrigerate for an hour or overnight.
Cut 3-4 pluots in half and then cut into thick slices, removing the pits as you do so. Toss with 2 T. sugar and 1 T. lemon juice. Let stand for 30 minutes or refrigerate until you’re ready.
Preheat the oven to 400 degrees.
In an oven-proof skillet or cast iron pan, melt 6 T. butter and add 1/2 C. sugar. Stir to melt the sugar into the butter.
Arrange the plum slices in concentric circles over the sugar/butter mixture in a tightly packed single layer. Do not add additional layers even if you pluots leftover. Cook for 20-30 minutes, pressing the plums down gently but not stirring, until a deep red liquid forms. Remove from heat and allow to cool for 10 minutes.
Roll out the dough over plenty of extra flour so it doesn’t stick. It should be big enough to cover the pan with some overhang. Slide it over the pan and tuck it in at the edges. Cut several slits in top to allow steam to escape.
Bake for 30 minutes, until the crust is golden brown and the edges are bubbling. Allow to cool enough so you can touch the pan, but do not refrigerate.
For the best presentation, place a plate over the top of the pan. Hold the plate firmly against the pan and then simultaneously invert both. The tart should slip out of the pan with the crust underneath.