Preheat the oven to 400˚F (200˚C).
Spread the onion on a baking sheet and drizzle with the olive oil. Roast for 15-20 minutes, until the onion is slightly charred. Let cool to room temperature, then roughly chop and transfer to a medium bowl.
To the bowl, add the mayonnaise, sour cream, Hearty spice blend, salt, and lemon juice and whisk to combine.
Serve the onion dip with chips.