Preheat oven to 350°F (175°C). Grease and flour a 10-inch bundt pan thoroughly.
Beat butter and sugar for 3–4 minutes until light and fluffy.
Add eggs one at a time, beating well after each. Scrape the bowl as needed.
In a separate bowl, whisk flour, baking powder, baking soda, and salt.
Add dry mix to the butter mixture in parts, alternating with buttermilk. Don’t overmix.
Stir in strawberries, drained pineapple, and vanilla gently.
Pour batter into pan. Bake 60–70 minutes, until a toothpick comes out clean.
Cool in the pan for 10 minutes, then turn out onto a rack to cool completely.