Peanut Butter Swirl Bars

Preheat oven to 350°F. Line an 8x8-inch pan with parchment paper. Set aside.

Sift together flour, baking soda, and salt into a bowl. Set aside.

Melt butter in a small saucepan or in the microwave; transfer to a medium bowl. Mix in sugar and vanilla. Stir in egg. Add mixture to dry ingredients and mix until no streaks of flour remain. Pour batter into prepared pan.

Make the peanut butter swirl: mix together peanut butter and sugar in a small bowl until smooth. Add egg and stir until combined. Spoon mixture on top of batter and swirl using the tip of a knife.

Bake for 25 to 30 minutes, or until a toothpick inserted in the center comes out with moist crumbs. Let cool completely before cutting into squares.