[Python] How to pass variables to a template HTML with Flask

i'm currently learning Flask templates, but i can't undestand how to pass a variable to it. Example of my Python code:

from flask import Flask

app = Flask(__name__)

@app.route('/')
def home():
return {"message":"on"}, 200

@app.route('/user/<string:username>')
def user_profile(username):
return render_template('profile.html')


My profile.html:

<!DOCTYPE html>
<html>
<head>
<title>Perfil</title>
</head>
<body>
<h1>User: (username)</h1>
</body>
</html>

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