Trump brushes off Ocasio-Cortez. She responds by hitting the president where it hurts.

Freshman Democratic Rep. Alexandria Ocasio-Cortez hit President Donald Trump where it hurt on Monday — mocking his wealth — after the president had dismissed her recent comments about him with a "who cares?"

Trump was asked on the White House lawn about Ocasio-Cortez calling him a racist during a "60 Minutes" interview earlier this month in which the New York lawmaker said there was "no question" the president was racist. Trump responded, "Who cares?"

Ocasio-Cortez took to Twitter to respond soon after.

In a follow-up tweet, Ocasio joked that the 70 percent marginal tax rate she suggested be implemented on earning in excess of $10 million would not apply to Trump — who claims to be a billionaire — because he "probably hasn't made more than $10 million in years."

She added that's probably why he's refused to make his tax returns public.

Ocasio-Cortez has watched her stock skyrocket in the Democratic Party since pulling off a surprising upset over longtime Democratic Rep. Joe Crowley last summer. She has built up a large social media following and has been unafraid to challenge leadership in her own party.

Last week, the 29-year-old lawmaker issued an impassioned response on MSNBC to Trump's national address calling for wall funding to end the government shutdown.

Days later, Trump told reporters the Democratic Party had been "taken over by a group of young people who, frankly, in some cases, I've been watching, I actually think are crazy."

Trump claimed to have predicted Ocasio-Cortez's victory over Crowley in an August interview with Bloomberg.

"So I’m watching television and I see this young woman on television and I say, 'Who’s that?'" Trump said. "Oh, she’s campaigning against Joe. You know who Joe is, right? Queens. Crowley. So, I say, ah, let me just watch her for a second. Wonderful thing, TiVo. So you go back. Hah. Tell him he’s going to lose."

"Now, I don’t agree with her views," he added. "Her views are terrible."

A study published by Axios on Sunday showed that Trump and Ocasio-Cortez drove the most engagement on Twitter by far among all U.S. politicians during the past month.