Find unique entries with a unique attribute in a table

I have a schema in which one key associated with many rows:

group: assignment
Person = {
name,age,gender
'Ben',21,'male'
'Cal',33,'male'
'Dan',13,'male'
'Eli',45,'male'
'Fay',21,'female'
'Gus',24,'male'
'Hil',30,'female'
'Ian',18,'male'
}
Eats = {
name,pizza
'Amy','mushroom'
'Ben','pepperoni'
'Ben',cheese
'Cal','supreme'
'Dan','pepperoni'
'Dan','cheese'
'Dan','sausage'
'Dan','supreme'
'Dan','mushroom'
'Eli','supreme'
'Eli','cheese'
'Fay','mushroom'
'Gus','mushroom'
'Gus','supreme'
'Gus','cheese'
'Hil','supreme'
'Hil','cheese'
'Ian','supreme'
'Ian','pepperoni'
}
Frequents = {
name,pizzeria
'Ben','PizzaHut'
'Ben','ChicagoPizza'
'Cal','StrawHat'
'Cal','NewYorkPizza'
'Dan','StrawHat'
'Dan','NewYorkPizza'
'Eli','StrawHat'
'Eli','ChicagoPizza'
'Fay','Dominos'
'Fay','LittleCaesars'
'Gus','ChicagoPizza'
'Gus','PizzaHut'
'Hil','Dominos'
'Hil','StrawHat'
'Hil','PizzaHut'
'Ian','NewYorkPizza'
'Ian','StrawHat'
'Ian','Dominos'
}
Serves = {
pizzeria,pizza,price
'PizzaHut','sausage',12
'PizzaHut','cheese',9
'PizzaHut','supreme',12
'LittleCaesars','pepperoni',10
'LittleCaesars','sausage',10
'LittleCaesars','cheese',7
'LittleCaesars','mushroom',9
'Dominos','cheese',10
'Dominos','mushroom',11
'StrawHat','pepperoni',8
'StrawHat','cheese',9
'StrawHat','sausage',10
'NewYorkPizza','pepperoni',8
'NewYorkPizza','cheese',7
'NewYorkPizza','supreme',9
'ChicagoPizza','cheese',8
'ChicagoPizza','supreme',9
}

I'm trying to find the pizzerias that have only female or only male frequents. How do I get pizzerias that have only 1 entry in π gender, pizzeria (Person ⨝ Frequents)?

Output:

{
    "Person.gender","Frequents.pizzeria"
    "male","PizzaHut"
    "male","ChicagoPizza"
    "male","StrawHat"
    "male","NewYorkPizza"
    "female","Dominos"
    "female","LittleCaesars"
    "female","StrawHat"
    "female","PizzaHut"
    "male","Dominos"
}

Find all pizzerias that are frequented by only females or only males.