Cocoa and pureed raspberries add natural sweetness to these pretty brownies, allowing us to cut back on the added sugar.
Cook raspberries in a small saucepan over medium-low heat, stirring and crushing them with a fork, until broken down, 2 to 4 minutes. Transfer to a mini food processor. Add cashew butter and water; puree until smooth. Set aside.
Combine chocolate, butter and oil in a stainless-steel bowl. Set the bowl over a saucepan of gently simmering water and melt the ingredients together. Remove from heat and stir to combine. Let cool for 20 minutes.
Meanwhile, preheat oven to 325°F. Coat a 9-inch-square baking pan with cooking spray. Line the bottom with parchment paper and coat the paper with cooking spray.
Combine eggs, sugar, vanilla and salt in a large bowl. Beat on medium-high speed until thickened and lighter in color, 3 to 5 minutes.
Whisk all-purpose flour, whole-wheat flour and cacao (or cocoa) in a medium bowl. Fold the dry ingredients into the egg mixture in 3 additions until most of the flour is incorporated. Add the melted chocolate mixture and stir until well combined.
Spread the batter in the prepared pan. Drop the raspberry mixture in 12 dollops over the batter. Drag a knife through the dollops and batter in an S-like pattern from one corner to the other. Turn the pan clockwise and repeat.
Bake until the brownies are firm to the touch, 25 to 30 minutes. The center will still be a bit shiny. Let cool on a wire rack for 20 to 30 minutes. Run a knife around the edges before cutting into 16 pieces.
Refrigerate for up to 4 days.