Preheat your oven to 350°F (175°C). Line a 12x17-inch half baking sheet with parchment paper, leaving extra overhang on the sides.
In a small bowl, sift together flour, baking powder, and salt. Set aside.
Separate the egg yolks and egg whites in two large bowls. Use a hand mixer or stand mixer on high to beat the egg whites until they form soft peaks. Set aside.
Move on to the bowl of egg yolks and beat on high for about 5 minutes. Gradually add the sugar, continuing to beat until fully incorporated.
Add the vanilla extract and mix just until combined.
Gently fold in the flour mixture in batches using a rubber spatula. Then fold in the beaten egg whites. Finally, gently add in 1/2 cup raspberry jam. Be careful not to deflate the batter.
Pour the batter into your prepared pan and spread it evenly.
Bake for 10-12 minutes, or until the top springs back lightly when touched and the edges are lightly golden.
While the cake bakes, lay out a clean kitchen towel and dust it generously with powdered sugar.