This is one of those “lemme pat myself on the back” recipes. The first time I tasted it I actually squealed with excitement. The zingy ginger and deeply aromatic fecks of vanilla bean are pretty spectacular, and just the right match for the complex, sour favor of the rhubarb. The pastry is also something to swoon over. It’s perfectly flaky, which I attribute to a few factors: adding buttermilk to the dough, freezing the butter cubes, and chilling the pastry a second time after it’s rolled out. Once you master the method, you’ll want to use it again and again—and you can, all year long with just about any fruit that’s in season.