No they cannot, as US imposes sanction on any country that defies the embargo, so Cuba ends up trading with those that couldn't care less about US embargos.
"Certain jurisdictions, such as the European Union and Canada, have so-called blocking statutes in place that are intended to mitigate the impact of U.S. sanctions on their citizens or entities conducting (in their view) legitimate business in Cuba."
https://www.skadden.com/insights/publications/2019/05/under-...
https://webgate.ec.europa.eu/isdb_results/factsheets/country...