Use nonstick baking spray on an 8x8-inch pan and set to the side. Preheat the oven to 350 degrees F. For the first layer of the cake, add the sugar, flour, baking powder and salt into a large mixing bowl. Mix to combine. Set to the side.
Zest both lemons and set zest to the side. Then juice both lemons into a medium bowl. To the lemon juice add the milk, eggs, oil and half the lemon zest. Use a fork to gently mix. Add this mixture to the dry ingredients and blend. Pour the batter into the bottom of the 8x8-inch pan.
For the second layer combine sugar, flour, the second half of the lemon zest. Sprinkle this mixture over the batter then pour the hot water over the top. Do not stir the water in.
Bake the cake for 30 to 34 minutes. The edges will be light brown but the center will remain a bit loose. Remove and cool for 10 minutes.
If desired, sprinkle the cake with powdered sugar.
