For Debra Allen, owner of Sweet Delights Bakery, the ultimate key lime pie filling ingredients are a well-kept secret, one she's guarded since starting the business in 2010 after dreaming up the ultimate dessert to save her struggling business. The only ingredient the self-taught baker is giving away: fresh, hand-squeezed key lime juice. By now, everyone knows the second most important ingredient to these key lime pies is also a ton of locally-grown, tropical fruit. They are available in a rainbow of flavors from tamarind, guava, and ginger to mamey and mango. These additions are just enough to lend a hint of color and a tang of flavor, but won't overwhelm the delicate key lime. Today, Allen's traditional, meringue-topped key lime pie remains the most popular - a hefty slice of creamy, pudding-like custard cradled in a paper-thin butter-and-graham-cracker crust. You can opt for a regular slice with or without the tufted crown of fluffy meringue. It's literally the stuff dreams are made of.