Fail!!

I don't want to put this on my blog, but as I mentioned in my first ever post for this challenge - all recipes tried regardless of how they turn out, will go up here.
The one thing I can be proud of is that I can bake. I can cook excellent cakes and cookies, in fact a lot of the time I make my own recipe up. So to have a cake FAIL as badly as this one did has me completely stumped as to what went wrong.

Marble Cake

3 eggs
3/4 cup sugar
1 cup plain flour
1 tsp baking powder
50g butter melted
2 tbsp boiling water
1 tbsp coca
2 to 3 red food colouring.

METHOD

1. Beat eggs until thick. Gradually beat in sugar until mixture is very thick and white.
2. Sift flour and baking powder together and then fold into egg mixture.
3. Fold in butter and boiling water.
4. Divide mixture into three equal parts. Into one-third stir the cocoa, to the another third the red food colouring and leave the last third plain.
5. Spoon the mixture in diaginal stipes into a greased and lined 20cm square cake tin. 
6. Using a knife twirl together the three mixtures. 
7. Bake at 190c for 20-25 minutes or until the cake springs back when lightly touched. Leave in tin for 10 minutes before turning out onto a wire rack. 

It's such a simple recipe so I am completely baffled as to why it failed like it did. I did try a new tin (one of those silicone ones) this time- wondering if the heat of a normal tin dissipates with these silicone ones so it doesn't get so hot? Going to have to try my neverfail cake and then at least I will be able to work out what went wrong.