API Gateway Cache Per-Key Invalidation

I need to invalidate an specific cache key from API gateway with a fire and forget request from another lambda (the one that handles the PUT request).

I’m having trouble to correctly set the permission described here
The role needed is this one below, and I’m setting this in the iamRoleStatements section of the update function.

  "Version": "2012-10-17",
  "Statement": [
      "Effect": "Allow",
      "Action": [
      "Resource": [

But I don’t know how to retrieve the resource arn.

If someone could help me, it would be great.