We love lemon. (Ooh, Ma’s Lemon Sponge Pie, with its tart curd and divine fluff.) And we love blueberries. (Ahh, Jordan Marsh Blueberry Muffin Cake, all juicy and sugar-crusty on top.) So it’s no wonder we love this moist Lemon Blueberry Swirl Cake. Sweet and tangy, it balances the two flavors just right. It makes a perfect snack cake or dessert. But its real secret to success? No need for fresh or even frozen berries. You’ll need lemons of course—but that’s easy, since you may have lemons in your fridge right now. We always keep a stash for lemon pasta, fish, scallopini, hummus…you name it. So we can toss together a lemon dessert just…