Place sugar in large bowl. Cut vanilla bean in half lengthwise. Using tip of paring knife, scrape out seeds and add to sugar. Discard vanilla bean (or reserve for other use).

Add eggs to sugar and whisk until smooth. Whisk in flour, baking powder, and salt until smooth (batter will be thick).

Using mandoline, slice 1 side of 1 apple ⅒ inch (2 ½ millimeters) thick until you reach core. Turn apple 90 degrees and slice until you reach core. Continue on remaining 2 sides; discard core. Reserve 18 well-shaped slices for top. Add remaining slices to batter and fold gently to coat. Set aside for 15 minutes.

Meanwhile, adjust oven racks to middle and lower-middle positions. Line rimmed baking sheet with aluminum foil or parchment paper, place on lower rack to catch drips, and heat oven to 350 degrees. Grease 8 ½ by 4 ½-inch loaf pan with vegetable oil spray. Line with 8 by 12-inch piece of parchment, smoothing so parchment is flush with pan sides and letting excess hang over long sides of pan. Lightly grease parchment.

Stir apple mixture, breaking up clumps of slices as needed (batter will have loosened) until all apple surfaces are lightly coated.

Using large slotted spoon, lift about ¼ cup of apples, letting excess batter drain back into bowl. Transfer apples to prepared loaf pan, keeping most apple slices flat (it's OK if some fold) and leveling with back of spoon. Continue until all apples have been transferred to pan and 2 to 3 tablespoons of batter remains in bowl.

Dip 1 side of reserved slices in remaining batter and shingle, batter side down, in rows of 3 slices on top of cake. Press firmly on apples with back of spoon to level. Spread any remaining batter over top and smooth with back of spoon. Bake on upper rack until top is well browned and apples can be easily pierced with skewer, 1 ½ to 1 ¾ hours, rotating pan halfway through baking. Transfer to wire rack.

Run knife around each short side of cake. Brush top with melted jelly. Let cool for 1 ½ hours (cake will deflate). Using parchment as sling, carefully lift cake out of pan and place on rack. Let cool completely, at least 2 hours.

Combine cream, sugar, and cinnamon in stand mixer fitted with whisk attachment. Whip on medium-low speed until frothy, about 1 minute. Increase speed to high and whip until soft peaks form, 1 to 3 minutes. Using sharp chef's knife, slice cake and serve with cream.