Using a little olive oil, lightly and evenly grease a small baking sheet or a large piece of waxed paper lying flat on a work surface. Keep the greased surface nearby while you work at the stovetop.
In a small saucepan over low heat, heat the milk warm, but not bubbling.
In a second small saucepan over low heat, combine the egg yolks, sugar, and vanilla. Using a wooden spoon, stir constantly until well combined, about 2 minutes. Add the flour, milk, and lemon zest and continue slowly stirring. Be sure to use the wooden spoon to clean the bottom of the pan with every few stirs to avoid letting any egg cook and congeal to the bottom of the pan. Turn the heat to a gentle medium and continue stirring slowly until the mixture thickens and forms a very dense homogenous pastry cream, about 5 minutes.
When the cream has thickened gently pour the cream onto the prepared work surface. Using a spatula, spread the cream so that it forms 1 layer 1-inch thick. Chill for at least 2 hours or overnight until firm.
When the cream has cooled, use a sharp knife to cut the layer of cream into 2-inch shapes (circles or squares).
Fill a deep pot no more than halfway with extra-virgin olive oil. Heat oil over medium-high heat until it reaches a temperature of 350 degrees F. The oil should remain at or around this temperature throughout the cooking process.
While the oil is heating, place the some flour, the egg whites and the bread crumbs in separate shallow bowls. Carefully dredge the cream circles 1 by 1 through the flour, then the egg whites and then the bread crumbs. Working in batches of 6, fry the fritters until golden brown. Use a slotted spoon or spider to gently drop the fritters into the oil, being careful not to splatter. Using the same spoon or spider, remove the finished fritters to a serving plate. Repeat process until all the crema fritta are cooked. Sprinkle with powdered sugar and serve.