Query with match by multiple fields

You need two match queries enclosed in a bool/must query, like this:

{
  "query": {
    "bool": {
      "must": [
        {
          "match": {
            "name": "n"
          }
        },
        {
          "match": {
            "tag": "t"
          }
        }
      ]
    }
  }
}