A FEW THINGS YOU'LL WANT TO KNOW
Can I make these ahead of time?
Yes, and I'd actually recommend it — bake the cake a day ahead and keep it wrapped in plastic or in an airtight container at room temperature, no need to chill it. Ice the squares closer to when you're serving them so the icing stays fresh and holds its swirl.
Why did my cake sink in the middle?
This usually comes down to a bit too much rise happening at once, the oven door being opened too early, or simply an underbaked centre — that last one is the most common culprit, so give it the full bake time and check with a skewer in a couple of spots, not just the centre, before pulling it out.
Can I make the icing ahead of time?
Yes — it keeps well in the fridge for up to five days. Just bring it out to room temperature and give it a good whisk by hand before using, so it comes back to that thick, light consistency.
Can I use buttercream instead of the whipped icing?
You can — a cream cheese buttercream will hold its shape for longer at room temperature and pipe with neater edges, if you're serving these somewhere warm or need them to sit out for a while.
Is this recipe nut-free?
Yes — nothing in the cake or the icing contains nuts, which makes this one I can always put out without worrying about who can and can't eat it.
What's the difference between gel and other red food colouring?
Gel colouring is much more concentrated than liquid, so you get a deep, true red without adding extra liquid to the batter. Liquid colouring needs a lot more to get the same depth of colour, Either works, but how much you use really comes down to how red you want the cake — start with less and add more until you're happy with the colour.
Why don't you beat the oil in with the butter and sugar?
Butter is solid, so creaming it with sugar traps tiny pockets of air, which is what gives the cake its lift and structure. Oil doesn't have anything for the sugar to catch onto, so beating it in at that stage won't add any lift — it just thins out the butter and takes away from what the creaming is doing for you. That's why the oil goes in separately, mixed through the buttermilk instead, where its job is to keep the crumb moist rather than help it rise.
Why does the oil separate a bit when I whisk it into the buttermilk?
A little separation is completely normal — oil and buttermilk don't fully blend the way two water- based liquids would, since one's fat and the other's mostly water. You're not aiming for a perfectly stable mixture, just an even distribution so the oil doesn't pool in one spot once it's in the batter. As long as you whisk it together and add it to the batter fairly quickly, it works fine.
I've seen others use sour cream instead of buttermilk — can I do that here?
You can, but it'll change the texture a little. Buttermilk's tang is what reacts with the baking soda for lift, so swapping it out entirely can make the rise less reliable. Sour cream is thicker and richer, so it's better used alongside the buttermilk rather than instead of it — that's what gives you a denser, more velvety crumb without losing the lift buttermilk provides
