Help me with my Save function, please?

Component

<aura:component controller="MyCustomSettingsController">
	<aura:handler name="init" value="{!this}" action="{!c.doInit}"/>
	<aura:attribute name="CustSettings" type="MyCustomSettings__c"/>
	<div class="divform">
		<form>
			<table>
				<tbody>
					<tr>
						<td>
							<span class="slds-text-heading--small">Client Key</span>
							<lightning:input type="text" aura:id="clientKey"
											 name="client"
											 value="{!v.CustSettings.Client_Key__c}"/>
						</td>
						<td>
							<span class="slds-text-heading--small">Secret Key</span>
							<lightning:input type="text" aura:id="secretKey"
											 name="secret"
											 value="{!v.CustSettings.Secret_Key__c}"/>
						</td>
					</tr>
				</tbody>
			</table>
			<div class="slds-grid">
				<lightning:button aura:id="save"
								  label="Save"
								  class="slds-m-top--medium"
								  variant="brand"
								  onclick="{!c.btnSave}"/>
			</div>
		</form>
	</div>
</aura:component>

JS Controller

({
	doInit : function(component, event, helper) {
		var action = component.get("c.getCustomSettings");
		action.setCallback(this, function(response) {
			var state = response.getState();
			console.log(state);
			if (state === "SUCCESS") {
				var returnVal = response.getReturnValue();
				component.set("v.CustSettings", returnVal);
			}
		});
		$A.enqueueAction(action);
	},
 
	btnSave : function(component, event, helper) {
        var CustSettings = component.get("v.CustSettings");
		var action = component.get("c.saveCustSettings");
        action.setParams({"Cust_setting" : CustSettings});
        action.setCallback(this,function(response){
			var status = response.getState();
            if(status === "SUCCESS"){
				var msg = 'Changes saved!';
                var toastEvent = $A.get("e.force:showToast");
                toastEvent.setParams({
                    title	: "Success!",
                    mode	: 'pester',
                    duration: '3000',
                    message	: msg,
                    type	: 'success'
                });
                toastEvent.fire();
			}
		});
		$A.enqueueAction(action);
    }
})

public with sharing class MyCustomSettingsController {
	@AuraEnabled
    public static MyCustomSettings__c getCustomSettings() {
       MyCustomSettings__c query = [SELECT Id, Client_Key__c, Secret_Key__c
                FROM MyCustomSettings__c];
        return query;
    }
    @AuraEnabled
    public static void saveCustSettings(MyCustomSettings__c Cust_setting){
        
        MyCustomSettings__c Custsetting = new MyCustomSettings__c();
        Custsetting = Cust_setting;
        update Custsetting;
    }
}