Preheat the oven to 350 degrees F. Butter an 8-inch-round cake pan, then line the bottom with parchment paper; butter the parchment and dust with flour, tapping out the excess.
Make the cake: Whisk the flour, granulated sugar, baking powder and salt in a medium bowl until combined. Whisk the melted butter, vanilla bean paste, eggs, milk and lemon zest in a medium bowl until just smooth. Add the wet ingredients to the dry ingredients and stir with a wooden spoon until incorporated. Pour the batter into the prepared pan and bake until a toothpick inserted into the middle comes out clean, 35 to 40 minutes. Transfer to a rack and let cool 10 minutes in the pan, then turn out of the pan onto the rack and let cool completely.
Meanwhile, make the toppings and filling: Halve 16 strawberries. Whisk 1 tablespoon water and the strawberry jelly in a medium bowl until smooth. Add the halved strawberries and toss to coat; set aside. Thinly slice the remaining strawberries, then toss with 2 tablespoons confectioners' sugar and the lemon juice in another medium bowl; set aside. Beat the heavy cream, the remaining 1 tablespoon confectioners' sugar and the vanilla extract in a bowl with a mixer on medium-high speed until soft peaks form. Refrigerate the whipped cream until ready to assemble. Carefully cut the cake in half horizontally with a serrated knife. Place the bottom half cut-side up on a platter. Drizzle the juices from the sliced berries over the cut sides of both cake halves. Fold a few tablespoons of the whipped cream into the sliced berries; spoon over the bottom cake layer. Cover with the other cake layer, then top with the remaining whipped cream. Top with the halved strawberries and their juices. Photograph by Anna Williams