By default your website lives at a Kavuo address. With Pro or higher you can use your own domain, for example yourrestaurant.com.
Connect it from Dashboard > Web > Edit > Domain and SEO (labelled "Dominio y SEO"): enter the domain, connect it, and Kavuo tells you the DNS record to add where you bought it. Once the DNS is verified, your site answers on that domain.
Your QR codes keep working if you change domain.
Kavuo does not sell domains: you need to own it already. Custom domains are not available on Start.
Open it in your dashboard