Cake. Grease an 8 inch round pan. Line it with parchment on the bottom and grease the parchment. Using 18 inch heavy duty foil, cut off a piece approximately 12 inches long and roll it up so that it becomes an approximately 1 inch thick, 18 inch long rectangle. Join the ends to form a circle. Place in the bottom of a large pot or Dutch oven. Pour water into the pot so that it reaches approximately ¾ of the way up the foil coil. Place prepared pan on top of the foil circle.
In a small bowl, whisk together the flour, baking soda, baking powder, salt, and poppy seeds. Set aside.
In a large bowl, press zest into the sugar to release the oils from the zest. Add eggs and whisk until thoroughly combined and mixture is somewhat lightened, approximately 30-60 seconds. Whisk in milk, sour cream, melted butter, vanilla, and lemon juice until thoroughly combined.
Add flour mixture to wet ingredients, mixing until just combined.
Pour into prepared pan. Cover pot and bring to a boil (usually takes 5-6 minutes for me), then reduce to a simmer. Steam for 30-45 minutes, waiting at least 25 minutes before opening the lid to check on it. Use a toothpick to check for doneness. The toothpick should come out clean and the edges of the cake should just start separating from the side of the pan. When done, turn flame off and uncover. Allow to cool approximately 15 minutes, then remove from pot and allow to cool on wire rack. Once fully cooled, use a metal spatula or knife to release the edges and remove cake from pan.
Glaze. Whisk together the confectioners sugar, cream or milk and 2 tsp. of lemon juice. If the glaze is too thick, continue to add some of the remaining lemon juice, ½ tsp. at a time, until the desired thickness is achieved. The consistency should be somewhat thick, but still pourable and spreadable. Pour over the cooled cake, using a metal spatula to spread it to the edges and allowing some of it to drip off the sides. Allow the glaze to harden at least 30 minutes before serving.
Store the cake in an airtight container at room temperature. It will keep for at least several days, although some of the glaze may get absorbed into the top of the cake. It is a delicious breakfast cake!