Prep your pan and oven: Heat the oven to 400°F (200°C). Line a 12-cup muffin tin with paper liners or grease lightly. High heat at the start helps lift the batter for domed tops.

Dry ingredients first: In a large bowl, whisk the flour, sugar, baking powder, baking soda, salt, cinnamon, and ginger. Break up any lumps so everything blends evenly.

Mix the wet ingredients: In a separate bowl or large measuring cup, whisk the oil, buttermilk (or yogurt), eggs, and vanilla until smooth.

Fold in the fruit: Add the diced mango and pineapple to the dry mixture and toss to coat lightly. This helps keep the fruit from sinking. Stir in the lime zest if using.

Combine gently: Pour the wet mixture into the dry. Fold with a spatula just until no dry streaks remain. The batter should be thick and slightly lumpy. Do not overmix or the muffins can turn dense.

Fill the cups: Divide the batter among the muffin wells, filling each about 3/4 full. Sprinkle the tops with turbinado sugar for a crunchy finish if you like.

Bake for lift, then finish: Bake at 400°F (200°C) for 5 minutes. Without opening the oven, reduce the heat to 350°F (175°C) and bake 12–15 minutes more, until the muffins are golden and a toothpick comes out with just a few moist crumbs.

Cool smartly: Let the muffins stand in the pan for 5 minutes, then transfer to a rack to cool. This keeps the bottoms from steaming and getting soggy.

Serve: Enjoy warm or at room temperature. They’re great plain, with a pat of butter, or a little honey.