[Vuejs]-Vuetify – How to handle click event on <v-btn>?

I recommend you to read VueJS Events Docs, in there you’ll get everything you need.
There’s an example of the docs:

<div id="example-2">
  <!-- `greet` is the name of a method defined below -->
  <button v-on:click="greet">Greet</button>
</div>

var example2 = new Vue({
  el: '#example-2',
  data: {
    name: 'Vue.js'
  },
  // define methods under the `methods` object
  methods: {
    greet: function (event) {
      // `this` inside methods points to the Vue instance
      alert('Hello ' + this.name + '!')
      // `event` is the native DOM event
      if (event) {
        alert(event.target.tagName)
      }
    }
  }
})

Do it this way;

<v-btn color="primary" rounded @click.prevent="startQuiz">Start</v-btn>

methods:{
     startQuiz(){
           console.log('start')
     }
}