Heat oven to 325°F. Line a 9x13-inch pan with parchment, leaving overhang.
Stir graham crumbs, crust sugar, and melted butter until evenly moistened.
Press mixture firmly into the pan. Bake 8–10 minutes. Cool while making filling.
Beat softened cream cheese on medium speed until very smooth, about 2 minutes.
Add filling sugar and beat until fluffy, scraping bowl as needed.
Mix in sour cream, vanilla, lemon zest, salt, and flour just until combined.
Beat in eggs one at a time on low speed. Do not overmix.
Pour filling over crust and smooth the top. Tap pan to release bubbles.
Bake 28–32 minutes until edges are set and center still slightly wobbles.
Cool 1 hour on a rack, then chill at least 3 hours. Lift out and slice.