It's a phrase used to express that someone is very attractive or impressive, literally "blinding" in their beauty or charisma.
Here's a breakdown:
* Nakaka - means "causes" or "makes"
* Silaw - refers to the feeling of being blinded by light
* Ka naman - is an intensifier, like "you are so..."
So, the phrase is literally saying "You cause/make me blind" but is used figuratively to convey how someone's attractiveness overwhelms you.