2 sticks unsalted butter, melted, plus more for greasing
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2 large eggs
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1 teaspoon vanilla extract
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1 ¼ cups all purpose flour
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¼ teaspoon baking soda
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½ teaspoon baking powder
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½ teaspoon kosher salt
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10 raspberries
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¼ cup raspberry preserves
Instructions
Preheat the oven to 375°F (190°C).
In a large bowl, whisk together the brown sugar, melted butter, and eggs until combined. Add the vanilla and whisk to incorporate.
In a separate large bowl, whisk together the flour, baking soda, baking powder, and salt. Add the wet ingredients to the dry ingredients and whisk to combine, being careful not to overmix.
In a small bowl, mash the raspberries with the back of a spoon or a potato masher until juicy. Fold into the blondie batter.
Grease an 8-inch square baking pan with butter, then pour the blondie batter into the pan and smooth the top.
Add the raspberry preserves to a microwave-safe bowl and melt in the microwave for 30 seconds. Pour on top of the batter, then use a toothpick or a skewer to create swirls.
Bake the blondies for 30–35 minutes, until a toothpick inserted in the center comes out clean.
Let cool completely in the pan before slicing into 9 pieces and serving.