(First off, Bellatrix didn't exist when Tom was at school, so let's just pretend she does.)

“Hi Tom,

I dare you to write a love letter to Bellatrix”

Why do you feel the need to humiliate me. Not only that, but Bellatrix needs no encouraging, as she is already completely obsessive over me. But if I must...

‘Dear Bellatrix,
Roses are red,
Violets are blue,
This rhyme may rhyme,
But it's not true,
Roses are Red,
That much is true,
But Violets are Violet,
Not bloody blue.

I hope you like the poem that I wrote for you, responding to the many similar ones I have received from you.
Yours Lovingly,
Tom.’

There. I sent it. I hope you're happy.

Yours,
Tom Riddle.