Welcome to the Cake Decorators Q&A

Could you please tell me which type of ganache would taste best with a zingy lemon sponge. Thankyou

Hi Kmmein

White ganache would be better but it is personal preference. I think the dark ganache would probably over whelm the flavour of the cake but you could try milk chocolate or even caramel or toffee. Personally I would use white chocolate buttercream with raspberry jam or raspberry coulis. I think white ganache on it’s own would be very sweet, you’d need something to cut the sweetness.
You’ll find the recipe for white chocolate buttercream for filling only here:

How to Make an Egg Free Cake + Vanilla Extract

Scroll down the page to see the recipe, this is enough to fill and cover an 8″ cake. This is not suitable to use a crumbcoate if the cake is to be covered with sugarpaste. White ganache would be suitable for the crumbcoat.
You could also add white ganache to buttercream and flavour it with extract of choice. See Paul’s recipe here:

Making and using buttercream

Hope this helps.