Cut butter into small pieces and return to the refrigerator to keep cold.
Preheat oven to 425°F (220°C). Line a baking sheet with parchment paper.
In a large bowl, whisk together flour, baking powder, sugar, salt, and lemon zest.
Add cold butter and toss to coat with flour. Use clean fingers or a pastry blender to work butter into the flour until the mixture resembles coarse crumbs.
Add frozen raspberries and gently toss to coat.
Drizzle heavy cream evenly over the mixture. Use a fork to gently mix, scraping from the bottom, until the dough begins to clump together.
Lightly knead in the bowl just until the dough forms a cohesive mass.
Transfer dough to the prepared baking sheet and gently shape into a 7–8 inch square about 3/4-inch thick.
Cut into 9 squares, then cut each square diagonally to form 18 triangles.
Space scones slightly apart and bake for 12–15 minutes, until lightly golden.