In a medium bowl, beat butter and sugar with an electric mixer until smooth and creamy, about 1-2 minutes.
Add egg and vanilla.
Beat until well incorporated.
Add flour, salt, and baking powder.
Mix only to blend.
Turn dough out onto a lightly floured piece of parchment.
Roll into a 9-inch x 11-inch rectangle.
Spread filling over entire surface of dough.
Starting with the long side, roll up jellyroll-style.
Wrap up in parchment, tucking ends under.
Refrigerate at least 2 hours.
When ready to bake, heat oven to 375℉/190℃.
Line 2 sheet pans with parchment paper. Set aside.
Slice dough roll into ½ inch slices.
Place on prepared sheet pans.
Bake for 12 minutes, or until just starting to color around the edges.