Brazilian natives Roberto and Tania Madeira opened a health food store in Key West in 1997. "We made the most boring, healthy food," Tania readily admits. That all changed when they won the city's Best Key Lime Pie contest in 1999 with a recipe handed down from Tania's 88-year-old grandmother. Suddenly they were loved. The Madeiras scrapped the tofu and veggies for limes, sugar, and meringue and opened a shop dedicated to the tartest of tarts. Since then they've been steadily marching north, opening another Key West locale, then one in Marathon. Last year they opened their South Miami shop, which is a shrine to the tiny green fruit. In addition to a swooningly good pie, they also sell lime juice, lime-covered chocolates, key lime salsa, and key lime honey-mustard dip. It's a cultural thing. "Brazil is the largest producer of key limes," Roberto says. "We call them limon galego. Our national drink, the caipirinha, is made with key limes." But the pie is the foundation of it all -- $16.25 for a plain pie, $17.25 for a chocolate-covered pie, and $18.25 for the signature, meringue-covered pie. Slices and frozen slices on a stick are $3.75.