1Heat oven to 350°F for shiny metal or glass pan (or 325°F for dark or nonstick pan). Spray bottom only of 13x9-inch pan with baking spray with flour.
2In large bowl, beat cake ingredients with electric mixer on low speed 30 seconds. Beat on medium speed 2 minutes, scraping bowl occasionally. Pour into pan.
3Bake 28 to 32 minutes or until toothpick inserted in center comes out clean. Cool 5 minutes. With handle of wooden/silicone spoon (1/4 to 1/2 inch in diameter), poke holes almost to bottom of cake every 1/2 inch, wiping spoon handle occasionally to reduce sticking.
4DO NOT MAKE IN ADVANCE (it thickens and you want it to ooze into holes)!!!! In medium bowl, stir together filling ingredients (mixture will thicken). Pour over cake; spread evenly over surface, working back and forth to fill holes. (Some filling should remain on top of cake.) Refrigerate 1 hour.
5Spread frosting over cake; sprinkle with lime peel. Garnish if desired.