• Preheat oven to 425℉ (220℃) conventional (see note 1 if using a convection oven) and line a 12-hole standard muffin tray with muffin liners. Set aside.

Streusel Topping

• To a small bowl, add flour, white granulated sugar, and salt. Mix until well combined.
• Add the melted butter and stir until the mixture is crumbly but slightly moist. Set aside (it will firm up in this time).

Raspberry Muffin Batter

• Sift together the flour, baking powder, and salt. Using a whisk, mix until well combined, then set aside.
• In a large bowl, combine the sugar, egg, butter, vegetable oil, milk, vanilla, lemon zest, and lemon juice. Using a whisk, mix until well combined.
• Add the pre-sifted dry ingredients to the wet ingredients, and using a spatula, gently fold until just combined. Do not overmix (see note 2).
• To finish off the batter, add in 1 cup (125g) of the raspberries and gently fold with a spatula until just combined. Do not overmix.
• Distribute the batter evenly among the muffin liners—they should be about ¾ full.
• Roughly mash the remaining half cup (62g) of raspberries with a fork, then place dollops on top of the muffins and swirl them slightly. You want it to be visible from the top.
• Finish by gently breaking up the streusel with your hands until you have large crumbs and evenly sprinkle the tops of the muffins with the streusel.
• Bake for 8 minutes at 425℉ (220℃). Then, without removing the muffins from the oven, reduce the temperature to 350℉ (180℃) and bake for an additional 12 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs (see note 3).
• Let the muffins cool in the tray for 10 minutes before transferring them to a wire rack to cool completely.