1Heat oven to 350°F (325°F for dark or nonstick pans). Place paper baking cup in each of 24 regular-size muffin cups.
2In large bowl, beat cupcake ingredients with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Divide batter evenly among muffin cups (about two-thirds full).
3Bake 18 to 23 minutes or until toothpick inserted in center comes out clean. Remove from pan to cooling rack. Cool completely, about 30 minutes.
4In medium bowl, mix frosting and 1/2 cup peanut butter. Frost cupcakes with frosting. Make a small indentation in center of frosting on each cupcake with back of spoon. Just before serving, spoon 1/4 to 1/2 teaspoon jelly into each indentation. Store loosely covered.