If you drive around Rhode Island in the summertime, you'll spot a green-and-white Del's Lemonade truck, emblazoned with a bright yellow lemon, on every corner, at every Little League game, alongside every public beach. Hundreds of college students earn tuition money by driving those little trucks, and serving up the famous iced lemonade to thirsty athletes and happy children. In the off season, you can buy Del's in the supermarket, in a cute plastic bucket filled with packets of the powdered mix, and that's the mix I use in the glaze for this lemon poppyseed cake. Sounds crazy, I know, but combined with real lemon juice, powdered lemonade adds a bit of fun, and an extra pop of lemon, to the icing. (You can use your favorite lemonade mix if you don't have Del's.) The basic sour cream cake recipe comes from Lorna, a reader who sent it to me along with a handmade ceramic cake pan. The cake isn't fussy, which suits my lack of natural baking ability, and it freezes well. Serve it with coffee or tea or -- why not? -- a glass of champagne.