Preheat your oven to 350°F (175°C) and prepare a 9x13-inch baking pan by greasing it or lining it with parchment paper.
In a large bowl, prepare the brownie mix according to the package instructions, typically requiring eggs, oil, and water. Pour the batter into the prepared baking pan and spread it evenly.
Bake the brownies in the preheated oven for about 25-30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. Do not overbake.
While the brownies are baking, combine the diced strawberries, granulated sugar, and lemon juice in a separate bowl. Toss gently to coat the strawberries and let them macerate for about 15 minutes.
Once the brownies are done, remove them from the oven and let them cool completely in the pan on a wire rack.
In a saucepan, heat the heavy cream over medium heat until it begins to simmer. Remove from heat and add the semisweet chocolate chips. Stir until the chocolate is completely melted and the mixture is smooth.
Spread the macerated strawberries evenly over the cooled brownies. Pour the chocolate ganache over the strawberries, ensuring they are well coated.
Allow the ganache to set at room temperature for about 30 minutes before slicing the brownies into squares.