Mix canola oil and grapefruit juice together, set aside.
Sift flour and salt twice together, set aside.
In a mixing bowl, add cold eggs and sugar, whisk at high speed for 3 mins, till thick and fluffy , medium speed for 10 mins and low speed for 1 min.
Continue beating at low speed, add in grapefruit zest and pulps, add flour spoon by spoon followed by canola oil and grapefruit juice. Do not over mix. Turn off machine and use a rubber spatula to fold the batter till well combined.
Pour batter into a lined 12 holes muffin pan until 90% full. Lightly tap on counter top twice to remove air bubbles.
Bake at pre-heated oven at 170C for 25 mins at middle rack of the oven.
Notes
Please keep in mind that all oven temperatures and baking time varies.
Recipe by Anncoo Journal at https://www.anncoojournal.com/grapefruit-sponge-cupakes/