In a bowl, mix together seasonal fruits of choice. Pour equal amounts of the fruit in each of the four jars. In another bowl, mix together flour, sugar, and salt until well combined. Pour equal amounts of dry ingredients on top of the fruit. Add 1 tbsp of butter on top of dry ingredients. Place the four jars into a square baking dish, a few inches apart. Spread dried beans around the jars to keep them steady while you’re moving them in and out of the oven. Bake at 350ºF for about 45 minutes. Remove from oven and allow cakes to cool down. When cooled, twist on lids and refrigerate until ready to serve. Top with a dollop of whipped cream.