Within the web GUI for a Tasmota device, head to Configuration > Configuration Other, and select 'Belkin WeMo' under Emulation. Give the device a useful friendly name, e.g., 'Porch' in the example below, and click 'Save'.

Then ask Alexa to discover devices: 'Alexa, discover devices'. Once Alexa answers that she (it?) has discovered your device, you can then say (e.g.): 'Alexa, turn Porch on', or 'Alexa, turn Porch off'.
If your Tasmota device is linked to Domoticz, then its status will be updated in the Domoticz web GUI.