Combine yeast, water, and eggs in bowl of stand mixer. Add sugar, flour, cinnamon, and salt. Mix with the paddle attachment for 2 minutes, to form a sticky batter. Scrape down, add butter, and mix on medium speed for 5 minutes. Scrape the very soft dough into a greased bowl, cover with plastic wrap, and chill in refrigerator for 12 hours, or overnight. Turn dough onto floured surface, roll out to ¼” and cut 1x1” squares. Arrange on floured parchment paper lined baking sheet and cover loosely with a clean, dry towel or plastic wrap. Let rest at room temperature while the oil heats up.
In an electric deep fryer or a medium sized pot heat oil to 350°F. Fry beignets, flipping once, until puffed and golden brown. Drain on paper towels. When cooled slightly, fit a small piping bag with an 1/8” diameter plain piping tip and fill with Lemon Curd. Fill each beignet with Lemon Curd, dust with powdered sugar and serve.