Preheat your oven to 350°F. Grease two 8-inch round cake pans, line the bottoms with parchment paper, and grease the parchment.
Using an electric mixer, beat the softened butter and caster sugar together on medium-high speed for 4-5 minutes, until very light, pale, and fluffy. Add the eggs one at a time, beating well after each addition.
In a separate bowl, whisk together the gluten free 1-to-1 baking flour, baking powder, and salt. Add the flour mixture to the butter mixture in three additions, folding gently with a spatula after each. Fold in the milk and vanilla extract until the batter is smooth and evenly combined.
Divide the batter evenly between the two prepared pans and smooth the tops. Bake for 22-26 minutes, until the cakes are golden and a toothpick inserted in the center comes out clean.
Let the cakes cool in the pans for 10 minutes, then turn them out onto a wire rack and peel off the parchment. Let them cool completely.
Whip the heavy cream, 2 tablespoons powdered sugar, and vanilla extract together with an electric mixer until firm peaks form.
Place one cake layer on a serving plate. Spread the strawberry jam evenly over it, then spread or dollop the whipped cream on top of the jam. Place the second cake layer on top and dust generously with powdered sugar. Serve at room temperature.