These thick, buttery snickerdoodle bars deliver everything you love about the classic cinnamon-sugar cookie — the crackly top, the tangy chew, the warm spice — without any rolling or shaping. One bowl, one pan, and they're done in under 45 minutes. The cream of tartar is non-negotiable; it's what gives these bars that signature snickerdoodle tang that sets them apart from a plain cinnamon blondie.
170g¾ cup / 6 oz unsalted butter, melted and cooled slightly
300g1½ cups granulated white sugar
2large eggsroom temperature
2teaspoonsvanilla extract
280g2¼ cups plain flour (all-purpose flour)
1½teaspoonscream of tartar
½teaspoonbaking soda
½teaspoonsalt
1teaspoonground cinnamon
Cinnamon Sugar Topping
2tablespoonsgranulated white sugar
1½teaspoonsground cinnamon
Instructions
Preheat your oven to 180°C / 350°F. Line a 23x33cm (9x13 inch) baking pan with parchment paper, leaving overhang on the long sides for easy lifting.
In a large bowl, whisk together the melted butter and sugar until well combined. Add the eggs and vanilla extract and whisk until smooth and slightly glossy.
Add the flour, cream of tartar, baking soda, salt, and cinnamon. Stir with a spatula until just combined — the dough will be thick.
Transfer the dough into the prepared pan. Use damp fingertips or a piece of parchment to press it into an even layer.
Mix together the cinnamon sugar topping and sprinkle evenly over the surface.
Bake for 22–26 minutes, until the edges are set and lightly golden and the centre looks just barely done — it will firm up as it cools. Do not overbake.
Cool completely in the pan before lifting out and slicing into 16 bars.
All temperatures stated are for conventional ovens. Decrease the temperature by 20°C/25°F or gas mark 1 for "fan" or air-fryers.