If I reduce the ingredients of a cake how much do I reduce the baking time?

[KatyMac]

Dropping Nigella's Brownies to a third as no-one needs that much cake when they live alone with their DH....

So I have the size of the tin correct for the reduction (I think) but how long should it bake for?

https://www.nigella.com/recipes/brownies

This one

Maybe half the time, it will definitely be more than a third of the tile. What is the size of the pan you're using?

I do brownies to about 75 C if you have a meat thermometer. If your recipe is less fudgy go to more like 85. Actual cake or bread needs around 100.

Her pan is 13 x 9 x 2.25, mine is 8 x 5 x 2

I dont have a thermometer currently, I broke it!

Roughly the same time if it’s the same depth. Maybe tweak by up to 5 minutes.

For example, a 20cm diameter Victoria sponge takes around 25 minutes. A dozen large cupcakes (much smaller diameter but similar depth) take 23 minutes.

Thanks @CheeseSandwichRiskAssessment & @JurassicClark

I agree with @JurassicClark - baking time is more about depth.

This recipe says 26-36 minutes but the recipe is for a 8 x 5 inch pan so that agrees also https://thecookiedoughdiaries.com/small-batch-brownies/#recipe

Do the Nigella recipe though, her brownies are the best!