How to create a grid of square buttons?

Hello,
I'm new to Xamarin and currently trying to move my Android activity to a Xamarin Content Page. The activity contains a grid (few linear layouts) of square shaped buttons of equal size - I would post a screenshot, but this page doesn't allow me to - ,,you have to be around for a little longer to post links"... That's also the reason why I had to remove xmnls references. That's pretty annoying to be honest.
I've written a following piece of XAML code:

    <?xml version="1.0" encoding="utf-8" ?>
    <ContentPage xmlns="..."
                 xmlns:x="..."
                 x:Class="TravelGuide.MainPage">
        <ContentPage.Content>
            <ScrollView>
                <Grid x:Name="MainGrid">
                    <Grid.RowDefinitions>
                        <RowDefinition Height="auto" />
                    </Grid.RowDefinitions>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                    </Grid.ColumnDefinitions>
                <Button Text="Text..."
                x:Name="btn1"
                VerticalOptions="CenterAndExpand"
                HorizontalOptions="Center"
                HeightRequest="{Binding Width, Source={x:Reference btn1}}"
                Grid.Row="0"
                Grid.Column="0"/>

                <Button Text="Text2..."
                x:Name="btn2"
                VerticalOptions="CenterAndExpand"
                HorizontalOptions="Center"
                HeightRequest="{Binding Width, Source={x:Reference btn2}}"
                Grid.Row="0"
                Grid.Column="1"/>

                <Button Text="Text3..."
                 x:Name="btn3"
                VerticalOptions="CenterAndExpand"
                HorizontalOptions="Center"
                HeightRequest="{Binding Width, Source={x:Reference btn3}}"
                Grid.Row="0"
                Grid.Column="2"/>
            </Grid>
        </ScrollView>
    </ContentPage.Content>

Unfortunately, it doesn't work if I put a long text inside of a button - the button automatically resizes to fit the text.
How to prevent that?