A simple recipe is often as good as a complicated one and this tart proves it. The pat-in-the-pan crumb crust and the one-bowl lemon filling come together in almost no time. And if you add the blueberries, (they require 15 minutes at most), you get a creamy, smooth, citrusy tart with a crown of sweet berries, as delightful to look at as it is to eat. Clearly, great results from little effort. Lemons vary in the amount and potency of their juice.