Meanwhile, in a large skillet, melt butter over medium-high. Add onion, season with salt and pepper, and cook until light golden, 8 to 10 minutes. In a medium bowl, whisk together eggs and cream. Add onion, bacon, and cheese and season with 1/2 teaspoon salt and 1/4 teaspoon pepper. Whisk to combine, pour into crust, and bake until center of quiche is just set, 40 to 45 minutes. Serve warm or at room temperature.