Char tortillas: if using a gas stove, place tortillas directly on stove above flame; cook, turning once, until tortillas puff and char in spots, 2 to 3 minutes total. (If using electric or induction stove, heat a large cast iron skillet over high heat until very hot; scatter water over tortillas using fingertips and cook tortillas in dry skillet until puffed and charred in spots, as if over gas flame in instructions above.) As tortillas become charred, enfold and stack tortillas in a clean kitchen towel.
Heat oil in a large skillet over medium-high. Add garlic, coriander and cayenne and cook 1 minute. Stir in lamb and cook, breaking up meat with a wooden spoon, until crispy and browned, 6 to 8 minutes. Season with salt, pepper and lemon juice. Divide meat among tortillas and top with feta and arugula.
Before her diagnosis, Caroline wrote a book on cakes called Cake Magic!. She started developing a birthday cake using her gluten-free mix found in that book. Check out other recipes she’s developing for her new life—and the stories behind them—on her blog, The Wright Recipes. Her next book, Catalan Food, written with chef Daniel Olivella, comes out in early September from Clarkson Potter.