Preheat your oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan.
In a large mixing bowl, combine the flour, sugar, baking powder, and salt. Mix well.
Add the softened butter, milk, eggs, and vanilla extract to the dry ingredients. Beat with an electric mixer on medium speed for about 2 minutes until smooth.
Pour the batter into the prepared baking pan and spread evenly. Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
While the cake is baking, prepare the roasted berries. In a baking dish, combine the mixed berries, granulated sugar, and lemon juice. Toss to coat. Roast in the oven for 15-20 minutes until the berries are soft and syrupy. Remove and let cool slightly.
Once the cake is done, remove it from the oven and let it cool in the pan for about 10 minutes. Using the handle of a wooden spoon, poke holes all over the cake.
Pour the sweetened condensed milk evenly over the cake, allowing it to soak into the holes.
In a separate bowl, whip the heavy cream with vanilla extract until soft peaks form. Gently fold in the roasted berries, reserving a few for garnish.
Spread the berry mixture over the top of the cake. Chill in the refrigerator for at least 2 hours to allow the flavors to meld.
Before serving, top with whipped cream and garnish with fresh berries.
Notes
For a chocolate twist, add ½ cup of cocoa powder to the dry ingredients for a chocolate poke cake.
Substitute the mixed berries with your favorite fruits like peaches or cherries for a different flavor profile.