Send a quick note that says: I heard you, I'm thinking, I'll come back to this.
I saw your message. I need time to think before I answer properly, but I want you to know I'm not ignoring it. I'll come back to this when I can respond with more care.
I hear you. I need a bit of time to think and I'll come back to this.
I care about this and I don't want to answer reactively. I need some time, and I'll come back to it with more care.