Brienne has been bullied for being different all her life. But still she's done what is right and stayed true to herself. Jaime has shown that he's seen that – seen her – every step of the way. This moment is the best possible way he could repay her for what she's done for him, and recognise her for who she is. A woman with honour. A knight of the Seven Kingdoms.
For Brienne, this is what she's wanted her whole life. For Jaime, it's a moment of honor for him, too. The fact that they're experiencing this together...well, frankly, it's more satisfying than any sex scene could ever be.