1 jar Morello cherries, also from Trader Joe’s. (It’s a good-sized jar but you use the whole thing.)
Thoroughly drain the cherries; do not rinse.
Prepare brownies as directed on package. Then carefully mix in drained cherries.
Pour batter into 8” x 8” (or larger) pan.
For 8" x 8" pan, bake in 350-degree oven for 40-45 minutes (brownies are pretty fudgy at 40 minutes so leave in oven longer if you like “cakier” brownies). A larger pan will require less time. Remove from oven when an inserted toothpick comes out clean.