Hi Ricardo,

I have gone through your question to send an email alert to contact when the task is created:- 
The below step is to send an email alert to the account owner when the task is created. You can do the same thing for contact also. Please try below step:-

Task is not in the list of objects where the Account Owner will work as a recipient on an Email Alert. The expected result here is the Email Alert will be sent to the Task Owner instead.

ResolutionBelow is the resolution to send an Email Alert to the Account Owner instead of Task Creator.

1) Create the Custom Email field on Task object:

Aloha: Click Setup | Customize | Activities | Activity Custom Field | New | Data type: Email | Name the field | Save.
Lightning: Click Gear icon | Setup | Object Manager | Activity | Field, and Relationships | New | Data type: Email | Name the field | Save.


2) Create the Process Builder On Task object.

Aloha: Click Setup | Create | Workflow & Approvals | Process Builder
Lightning: Click Gear icon | Setup | Process Automation | Process Builder
 
a) Click New, add the Process Name and select 'record changes' in The process starts when then Save 
b) Select the Task object
c) Evaluation Criteria: When the record is created or edited.
d) Add Rule Criteria with the condition: [Task].AccountId is null FALSE
e) Select the Advanced criteria option "Do you want to execute the actions only when specified changes are made to the record?"


3) Add an Immediate Action to the Process to update the Custom Email field: 

[Task].Account.Owner.Email​

4) Add a second Immediate Action to send the desired Email Alert:

5) Update the Email Alert to use the Custom Email field as the recipient.

6) Save and Activate the Process.

Please visit the link for reference:--  
https://help.salesforce.com/articleView?id=000319183&type=1&mode=1

I hope you find the above solution helpful. If it does, please mark as Best Answer to help others too.

Thanks and Regards,
Deepali Kulshrestha
www.kdeepali.com