How to parse a JSON column in Spark

Suppose you have a table with a string column that has JSON data encoded in it, like this one below, and you want to parse and query on the data of this column.

val df = Seq(
      ("{\"id\":1,\"amount\":{\"value\":60,\"currency\":\"BRL\"}}"),
      ("{\"id\":2,\"amount\":{\"value\":70,\"currency\":\"USD\"}}")
    ).toDF("my_json_col")