Brex, a fintech company that provides corporate cards and spend-management software to businesses, announced earlier today that it closed a $425 million Series D round of capital at a valuation of around $7.4 billion. The new capital came less than a year after Brex raised $150 million at a $2.9 billion pre-money valuation. So, how did the company manage to so rapidly boost its valuation and raise its largest round to date? TechCrunch spoke with Brex CEO Henrique Dubugras after his company’s news broke. We dug into the how and…