Using a lemon for only its juice is a big waste. The whole thing is edible, including the nutritious pith and the pulp, rich in fiber. Lemon zest is worth its weight in gold, and when I think about how much zest gets tossed, it makes me sad. How many meals could have been brightened? How many cookies pushed over the edge to greatness? I wouldn’t fault anyone for straining out the seeds, or cutting off the tip of the stem or blossom ends. But I’ve been putting everything else in the blender. The result is a foamy, lemon emulsion that is the solution to culinary problems that I didn’t even know I had. Blended lemon is like an enhanced form of lemon juice—thicker, and with a broader spectrum of lemon flavor. Like lemon juice, this lemon foam is equally at home in savory or sweet contexts, and is especially …