In a bowl, combine all the dry ingredients and whisk to combine.
In a seperate mixing bowl, add in the sugar, butter and oil and whisk till thoroughly combined.
Next, add in the eggs and whisk again until a thick smooth mixture forms.
Then, add in the lime zest, vanilla, vinegar and food colouring and whisk again to combine.
Next, add in the dry ingredients and buttermilk, alternating, beginning with the dry ingredients. With a spatula, fold in after each addition.
Finally, add in the lime juice and with the spatula lightly fold it in, making sure to have a smooth, airy batter at the end without overmixing.
Pour the batter into a 7 inch round cake pan (for a tall cake) that has been lined with parchment paper and greased around the sides.
Bake in a preheated oven at 325 degrees fahrenheit on the center rack for about 35 minutes.
The cake is ready when the top is still soft but set and is golden brown around the edges. Do the toothpick test as well.
Let the cake cool for 10 minutes in the pan, then take it out. Dust with powdered sugar and lime zest if desired and serve preferably warm. Enjoy!