Preheat oven to 350°F. Grease and flour three 8 ½-inch cake pans.
In a large bowl, combine oil, sugar, eggs, mashed bananas, and vanilla extract.
In a separate bowl, combine self-rising flour and salt. Incorporate dry ingredients into wet, stirring until just combined.
Pour batter into prepared pans. Bake for 20 minutes, then allow to chill completely before frosting.
To make frosting, whip butter and raspberry jam until light and fluffy, about 3 minutes.
Add in powdered sugar and milk and whip to combine, about 2 minutes.
Place first cake on a cake stand, then top with roughly 1 cup of frosting.
Layer second and third layers, frosting the same amount in between each.
Frost edges of the cake with remaining frosting, then top with fresh raspberries and garnish sides with edible flowers (optional).