Boutique investment banks are eating the lunch of Wall Street’s bulge-bracket firms.

The latest example: the mega-merger of H.J. Heinz and Kraft Foods, which left marquee firms on the outside looking in.

Centerview Partners, a New York boutique firm, was the sole adviser to Kraft Foods. Lazard was the only bank used by H.J. Heinz on the transaction. The deal—the largest merger in the first three months of 2015—is valued by Thomson Reuters at more than $46 billion.

Indeed, US boutique banks have doubled their share of M&A revenue since 2008, according to Dealogic. One reason is that cash-rich companies don’t require bank financing. At the same time, boutique firms have developed strong personal relationships with their clients, who have become repeat customers.

Meanwhile, large investment banks are stuck in neutral. Although worldwide M&A rose by 25% in the first quarter of the year—the strongest opening quarter for deals since 2007—investment banks failed to cash in. Global investment banking fees (from M&A advisory to capital markets) topped $20 billion in the first quarter. That’s a decrease of 8% from the first quarter of 2014. According to Freeman Consulting Services, the performance ranked as the slowest first quarter for fee-generation since 2012.