Prepare 3-7" cake pans with pan grease & parchment paper liner & preheat the oven to 350°F
Prepare the cake batter by melting the vegan butter then combine it with the vegetable oil
Combine the plant milk with the lime juice
In a large mixing bowl combine the flour, sugar, baking soda & salt then whisk together to incorporate all the ingredients very well.
Add the all liquids: That would be the plant milk with the juice & the melted vegan butter & oil then whisk smooth.
Add the lime zest & food color ~ whisk smooth
Divide the batter evenly between your prepared pans.
Bake immediately in a preheated 350°F oven for 25-30 minutes depending on the cake pans size & the thickness of the layers, but always check at around 20 minutes (3-7" pans took 28 minutes)
I like to do the "toothpick" test to make sure there is no raw batter in the centers before taking them out
Cool the cakes on a wire rack until you can safely touch them with your bare fingers then flip them out of the pans carefully to cool the rest of the way.
Make the simple syrup by bring the water & sugar to a boil in a small sauce pot then let it boil for 1 minute. Remove from heat & add the extract or mint oil, cool
Make the buttercream recipe according to the instructions on that recipe post & at the last stage of mixing add the rum or rum extract
Lightly brush each cake layer with the cooled mint syrup & build the cake with rum buttercream filling & icing.