1. Preheat oven to 350ยบ.
2. Cream butter and sugar together in a mixing bowl.
3. Add Dry ingredients + lemon zest, and mix until combined
4. Mix in the lemon juice, eggs and buttermilk. Mix on medium speed for 1-2 minutes.
5. Pour cake batter into greased 9x13 dish - after tasting! Bake for 28-34 minutes. Mine only took 28 minutes, but yours may need more time, depending on altitude, moisture, etc. I would bake for 28 and test with a toothpick.
6. While cake is baking, make your glaze. The glaze can be made by mixing the powdered sugar and lemon juice with a hand mixer.
7. While cake is baking, or ahead of time, make your candied lemons by boiling sugar and water in a small saucepan. As soon as mixture comes to a boil, add your thinkly sliced and seeded lemon. Simmer for 24 minutes. Remove lemon slices with a slotted spoon and place on wax paper to set.
8. Remove cake from oven and immediately poke a lot of holes with a fork. Then pour glaze over hot cake.
9. Garnish with candied lemons.