how to stretch the button to full fill the container

when i use react native button i cannot strech it, the blow is the style that i used for the button

myButtonStyle: {
     flex: 1,
     borderRadius: 5,
     alignSelf: 'stretch',
     backgroundColor: 5,
     borderWidth: 1,
     borderColor: '#007aff',
     marginRight: 5,
     marginLeft: 5
   }

and the button itself:

<Button
          style={myButtonStyle}
            title="Learn More"
            color="#841584"
            accessibilityLabel="Learn more about this purple button"
          />

and this is the style of the button wrapper

myCardSectioStyle: {
    borderBottomWidth: 4,
    padding: 5,
    backgroundColor: '#ffff00',
    justifyContent: 'flex-start',
    flexDirection: 'row',
    borderColor: '#6600ff',
    position: 'relative'
  }