To make the caramelized onions:

Melt olive oil and butter in large skillet over medium heat. Add onions and cook for 10 minutes, stirring occasionally. Stir in salt and sugar and reduce heat to medium low. Continue to cook for 45-60 minutes, stirring occasionally, until onions are a deep golden color.

To make the flatbread:

Preheat oven to 425 degrees.

Spread jam evenly onto flatbread. Layer half of onions onto flatbread. Crumble half of goat cheese over onions. Repeat with remaining onions and goat cheese. Bake for 8-10 minutes or until edges are crispy. Remove from oven and let cool for a few minutes. Cut into slices. Sprinkle basil on top of flatbread and add a generous pinch or two of flaky sea salt before serving.