Preheat the oven to 375F.
In a medium bowl, stir together the flour, sugar, baking powder and salt. Add the whipping cream and stir just until the dough comes together. Pat out on a lightly floured surface - a bit of flour will make it easier to handle, but don't work it into the dough - and cut into wedges or rounds, then transfer to a parchment-lined baking sheet. Dab the tops with a bit more cream (there should be just enough in the bottom of the measuring cup) and sprinkle with regular or coarse sugar, if you like. Bake for 15-20 minutes, until golden.
Meanwhile, thickly slice (if you need to) and toss your fruit or berries with sugar and let it sit to draw out some juices, or simmer them (in the case of rhubarb for sure) until soft with sugar to taste - I realize this can be tricky, but you can always add more sugar if it's too tart. You shouldn't need to add any liquid - just start the heat lower as the fruit softens and releases its juices. Whip the cream - as much as you like - with a spoonful of sugar and a bit of vanilla, if you like, and serve the fruit on the split shortcakes, topped with cream. Serves 6.