Preheat oven to 350 F. Butter and flour a 10 cup bundt pan.
Beat together the sugar, zest, , sumac, vanilla, salt and butter until very light and pale.
Add the eggs, one at a time, beating for a full 30 seconds before adding another.
In a separate bowl whisk together the flour and baking powder.
In another bowl whisk together the lemon juice and yogurt.
Add dry ingredients to mixer bowl and beat on low. Once it begins to incorporate add the wet ingredients.
Beat until the batter is fully mixed together, scraping the bottom to ensure all bottom bits are mixed in.
Scoop batter into prepared bundt pan. Smooth over the batter.
Bake for 45-55 minutes, until a toothpick comes out clean.
Let the cake cool briefly in the pan while you prepare the syrup. If you have a long thin cake tester like this, poke some holes in the cake.
In a small pot, cook together the sugar and lemon juice until the sugar is melted and the mix begins to boil.
Once it’s done, shut off the heat and pour the syrup over the cake while it’s still in the pan.
Let the syrup set into the cake for about 10 minutes. Then turn the cake over onto a cooling rack and pour the rest of the syrup on top.
Once cake is cool and syrup is set, dust with powdered sugar or make a glaze.