Prepare the batter: Preheat the oven to 350°F (175°C). Grease a 9x5-inch loaf pan and line it with parchment paper. Beat butter and sugar until fluffy, then mix in eggs one at a time. Stir in vanilla extract.
Mix dry ingredients: In a separate bowl, whisk together flour, baking powder, baking soda, and salt.
Combine wet and dry ingredients: Gradually mix the dry ingredients into the butter mixture, alternating with buttermilk. Stir until just combined—avoid overmixing.
Fold in fruit: Gently fold in drained pineapple and diced strawberries, ensuring even distribution.
Bake the cake: Pour batter into the prepared pan, smooth the top, and bake for 55-65 minutes. If the top browns too quickly, loosely cover it with foil for the last 10 minutes.
Cool the cake: Let it cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
Make the glaze: Whisk powdered sugar with 2-3 tablespoons of reserved pineapple juice until smooth. Adjust consistency if needed.
Garnish and serve: Drizzle glaze over the cooled cake, top with fresh strawberry slices.