Preheat the oven to 375°F, and set a 9x13 inch baking dish aside for the filling. Keep the oven fully preheated for even bubbling around the edges.

In a large bowl, combine the strawberries with granulated sugar, cornstarch, fresh lemon juice, vanilla extract, and cinnamon, then toss gently until coated. You should see the fruit shine as the dry ingredients cling.

Pour the strawberry mixture into the 9x13 inch baking dish. Spread it into an even layer so the filling bubbles consistently.

Whisk together all-purpose flour, baking powder, and salt in a separate bowl. Break up any lumps so the biscuit topping bakes up tender.

Cut in cold butter until the mixture resembles coarse crumbs. Stop when you still see small butter bits.

Stir in buttermilk until just combined. The dough should look thick and slightly shaggy, not smooth.

Drop spoonfuls of biscuit dough over the strawberry mixture, leaving some filling visible. Aim for uneven spacing so the fruit peeks through as it bakes.

Sprinkle coarse sugar over the top for a crisp, golden finish. Use a light, even layer so it caramelizes in the oven.

Bake for 40-45 minutes at 375°F until golden brown and the filling is bubbly around the edges. Look for a set fruit layer with bubbling visible near the perimeter.

Let the cobbler rest for 10 minutes before serving. This brief rest helps the filling thicken so each scoop holds together.