Preheat oven to 350°F (175°C). Grease an 8-inch square baking pan. If you like, line the pan with parchment paper before greasing.
Toss the chopped cherries in 1 tablespoon flour.
In a separate bowl, whisk together 1 cup flour and salt. Set aside.
Melt the chocolate and butter in the microwave at 30-second intervals until the butter is melted and the chocolate melts when stirred. Set aside to cool slightly.
In a large bowl, beat the sugar, eggs, and vanilla until smooth. Add the chocolate mixture, and mix until combined.
Gradually add the flour mixture, mixing just until combined. Stir in the cherries.
Spread the batter evenly in the prepared pan. Bake for 30 minutes, or until a pick inserted in the center comes out with moist crumbs.
Cool completely in the pan before cutting into bars.
Notes
Store dark chocolate sour cherry brownies in an airtight container at room temperature for up to 3 days. If you need to stack them in the container, I recommend placing parchment paper between the layers.