The Belgian, who joined Manchester United earlier this month for £75m, was making just his second appearance in a United shirt, having made his debut off the bench in their 5-2 win over LA Galaxy on Saturday evening.
The former Everton striker started the match, playing 45 minutes up top as Jose Mourinho opted to play a 4-3-3 formation with Lukaku as the focal point.
After Luis Silva gave the MLS side the lead with the opening goal of the match, Henrikh Mkhitaryan levelled the tie and Lukaku put United in front before half-time.
Armenia international Mkhitaryan was involved in the build-up to Lukaku's goal, as he slotted the ball through to the 24-year-old, who rounded goalkeeper Lalo Fernandez before cooly slotting the ball into the empty net.
Manchester United's USA tour rolls on as they now prepare to face Manchester City in Houston on July 20.
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