For the bread:
Preheat oven to 350°F. Generously butter a 9-by-5-inch loaf pan or line with a sheet of parchment.
In a large bowl whisk together the flour, sugar, baking soda, and salt.
In a medium bowl, whisk together the bananas, eggs, butter, buttermilk, and vanilla. Add the into the flour mixture and gently stir until just combined. Fold in the strawberries.
Pour batter into prepared loaf pan and smooth the top. Bake for about 1 hour, or until golden brown on top and the center springs back when gently pressed. Let cool on a wire rack for 30 minutes before removing from loaf pan to cool completely.
Banana bread can be stored tightly wrapped in plastic for up to 3 days at room temperature or 2 weeks frozen (thaw overnight at room temperature before serving).
For the buttercream:
In the bowl of a stand mixer fitted with the paddle attachment, mix together the sugar and butter. Mix on low speed until well blended and then increase the speed to medium and beat for another 3 minutes. Add the salt, vanilla, and preserves and beat on medium for 1 minute. Add in food coloring, if using.
Spread the buttercream over the top of the bread. Top with strawberries. Serve, or cover and store at room temperature for up to 1 day.