1. Heat 2 inches vegetable oil in a large deep pot over medium-high heat until it reaches 350ºF on a candy thermometer. (As oil is heating, watch thermometer carefully and adjust heat to keep oil from getting too hot.) Line a large plate with paper towels.
2. In a large bowl, stir together egg, sugar, ricotta, lemon zest, vanilla, flour and salt until smooth.
3. Drop heaping teaspoonfuls of batter into hot oil and fry, turning once with tongs or a slotted spoon, until beignets are golden, 2 to 3 minutes total. Remove beignets with a slotted spoon and place on a paper towel-lined plate briefly to drain. Dust with confectioners' sugar, if desired, and serve immediately.
Cook Time: 3 minutes per batch