Heat the Oven – Set the oven rack to the upper-middle position. Preheat to 425ºF (218ºC).
Prepare the Strawberries – Rinse and dry the strawberries. Cut into pieces, about ¼" in size. Measure out 1 ½ cups for the muffin batter and ½ cup for the topping.
Mix the Dry Ingredients – In a large bowl, whisk together the flour, baking powder, salt, and ½ teaspoon cinnamon.
Mix the Wet Ingredients – In a medium bowl, whisk together sugar and eggs until smooth and pale yellow in color, about 1 minute. Slowly whisk in the cooled, melted butter and vegetable oil until incorporated. Whisk in the buttermilk and vanilla.
Make the Muffin Batter – Add the egg mixture and 1 ½ cups of strawberries to the flour mixture. Gently fold the mixture until the flour is just moistened, with some lumps and flour spots remaining. Do not overmix the muffin batter.
Portion the Batter – Grease the muffin pan with nonstick cooking spray or vegetable oil. Alternatively, line with paper liners. Fill each opening to the top, about a ⅓ cup per muffin. Evenly distribute the reserved ½ cup of strawberries on top, lightly pressing in. In a small bowl, combine 1 tablespoon sugar and ⅛ teaspoon cinnamon. Evenly sprinkle over the top of each muffin.
Bake the Muffins – Bake for 10 minutes. Rotate the pan and bake until golden brown, 6 to 7 minutes. The center of the muffin should reach about 205 to 210ºF (96 to 99ºC).
Cool the Muffins – Cool the muffins in the pan for 5 minutes. Use a spatula to carefully remove them, then transfer them to a wire rack until ready to serve.
Notes
Using Table Salt: Add ¾ teaspoon of table salt instead of 1 teaspoon of kosher salt.
Buttermilk Substitute: Mix ½ cup sour cream or Greek yogurt with ½ cup milk. Whole milk yields a thinner batter, a lighter texture, and a different flavor.
Storing: Cool and store in an airtight container at room temperature for up to 4 days. Freeze for up to 3 months.
Reheating: If frozen, place the muffin on a paper towel and microwave until soft, 60 to 90 seconds.