1/2 cup butter, or margarine, cut into 4 pieces
6 tablespoons unsweetened cocoa powder
3/4 cup sugar
2 large eggs
2 tablespoons milk
1 teaspoon vanilla
2/3 cup all-purpose flour
1/2 teaspoon baking powder
1/4 teaspoon salt
1/2 cup chopped pecans, or walnuts
Place butter and cocoa in 8x8-inch baking dish. Microwave, uncovered, at High power until butter is melted, 1 to 1 1/2 minutes.
Add sugar to baking dish; stir to mix well. Add remaining ingredients; mix well, especially in corners. Spread batter evenly in dish.
Shield 4 corners of baking dish with aluminum foil triangles to prevent overcooking in corners.
Microwave, uncovered, at High power until top is no longer wet, 5 to 6 minutes; rotate dish 1/2 turn after 3 minutes.
Place baking dish directly on heatproof counter; let stand 10 minutes to complete cooking. Cut brownies into 2-inch squares.