A legal way for high earners to fund a Roth IRA despite income limits.
The backdoor Roth is a strategy for those whose income is too high to contribute to a Roth IRA directly: you contribute to a Traditional IRA and then convert it to a Roth. It is sensitive to the IRS pro-rata rule, which can create unexpected tax if you hold other pre-tax IRA balances, so it is worth confirming the mechanics before doing it.
A high earner contributes to a Traditional IRA, then converts it to a Roth shortly after.