Preheat your oven to 350°F (175°C). This ensures that the brie bakes evenly and reaches the ideal gooey consistency.
Melt 2 tablespoons of butter in a skillet over medium heat. Watch the butter closely to avoid burning.
Add 2 sliced medium apples, 2 tablespoons of brown sugar, 1 teaspoon of cinnamon, and 1 tablespoon of lemon juice to the skillet. Stir everything together to coat the apples in the mixture.
Cook the apple mixture for 5-7 minutes, stirring occasionally, until the apples are tender but still hold their shape. You want them soft but not mushy.
Place 1 round of brie cheese in a baking dish. Make sure the dish is oven-safe to prevent any spills.
Pour the sautéed apples on top of the brie, spreading them evenly over the cheese.
Bake in the preheated oven for 10-15 minutes, or until the brie is gooey and melted. Keep an eye on it to ensure it doesn't overcook.
Once baked, remove from the oven and cool slightly; this allows the cheese to set a little while still remaining warm.
Garnish with fresh thyme to elevate the presentation, and serve immediately with crackers or baguette slices. Enjoy!