What to do with heaps of Grapefruit? Not marmalade

We have a tree with an abundance of grapefruit on it.
Any ideas what to do with them - other than marmalade or for breakfast???
TIA

honestly we had a huge amount and i just juiced most of it and froze the juice....alternatively you can substitute orange for a small grapefruit in the below magical orange cake recipe....i havent done that but have been told you can.

Magical Orange Cake

1 whole orange, washed and processed to a pulp, (I pulp it first on its own to be gentler to my small food processer)
125gr melted butter,
1 cup sugar
2 med-lge eggs,
1 1/2 cups self-raising flour.

YES, ITS AS EASY AS IT LOOKS! If you have a food processor, just throw everything in together and mix till all combined.

If you don’t, and want to do it the old-fashioned way.
Mix together the melted butter and sugar, add egg then orange pulp. Stir to combine then fold in sifted SR flour.

Pour into lined loaf or cake tin and bake at 180C for approx 35-40 mins or ready when tested with skewer.

You can double this recipe - it made a lovely round tin cake which I ice with orange icing and also a loaf which can be left plain or drizzled with a syrup topping of orange juice and caster sugar heated in a pot until sugar is dissolved.

grape fruitspread1cup water1cup sugar1tlbsp butter1/2tsprind2tlbspcustard powder3/4cupjuiceputsugarwaterbuterandrindin panboilthenmixpowderto apastewithjuicetheaddtoliquidreturn toheatandcookafewmins

yes we juice heaps of them and freeze it. so refreshing in summer! bought a juicer from Briscoes. takes some of the hard work out of doing so many!

juice them and freeze the juice for summer :)

Grapefruit shortbread - just add some juice and finely grated rind to your normal recipe.

Grapefruit cordial. Make a sugar syrup of 1.5 l of water and 1.5kg of sugar. Stit over low heat until sugar is dissolved. Add juice of 8 grapefruit and 2 tbspn rind and 2 tspns tartaric acid. Bottle. Dilute approximate 10:1 with water, tonic water, sprite etc. Makes a fantastic summer drink with spruces, cordial, White rum, ice and a sprig of mint or lemon balm. Delicious!

Grapefruit juice and feijoa juice is really yummy.