Position the oven rack in the center of the oven and preheat to 500 degrees F. Whisk the buttermilk, eggs, salt, vanilla and 1/3 cup granulated sugar together in a large bowl until completely combined. Whisk the flour, baking powder and baking soda together in another large bowl until completely combined. Fold the buttermilk mixture into the flour mixture with a silicone spatula until just combined (it's OK if there are a few lumps). Reserve 2 tablespoons of batter in small bowl and set aside.
Brush 2 tablespoons butter on a 18-by-13-inch sheet pan and pour in the batter, using a spatula to smooth out the top. Tap the tray on the counter a few times to even out and flatten the batter.
Stir the warmed jam in a small bowl until pourable. Imagine the batter in the pan divided into four sections (2 across and 2 down). Dollop the jam, about 1 teaspoon at a time, over the surface of one section. (You want to see red dots of jam sitting on top of the batter.) Using a toothpick or small skewer, swirl the jam into the batter, making a marbled pattern. Top with sliced strawberries.
Sprinkle chocolate chips over a second section of the batter. Arrange banana slices in a herringbone pattern over a third section of the batter and sprinkle the fruit with the remaining 1 to 2 teaspoons granulated sugar.
Mix the brown sugar, cinnamon and reserved batter together in a small bowl, and dollop, about 1 teaspoon at a time, over the last section of the batter. (You want to see a lot of brown dots sitting on top of the batter.) Using another toothpick or small skewer, swirl the cinnamon mixture into the batter, making a marbled pattern.
Put the sheet pan in the oven and immediately reduce the temperature to 400 degrees F. Bake, rotating the sheet pan halfway through baking, until golden brown and a cake tester inserted into the center of the pancake comes out clean, 18 to 23 minutes.
Brush the pancake with the remaining 2 tablespoons butter and let cool 15 minutes before cutting. Stir together the confectioners' sugar and 1 teaspoon water in a small bowl and drizzle over the cinnamon swirl quadrant.
Serve the pancakes with maple syrup and whipped cream or sprinkle with powdered sugar. Use a mesh strainer to sprinkle for beauty!